Establishment of Normal ADC Values and Morphological Parameters of the Fetal Kidney Using Magnetic Resonance Imaging and Analysis of their Correlation with Gestational Age

Establishment of Normal ADC Values and Morphological Parameters of the Fetal Kidney Using Magnetic Resonance Imaging and Analysis of their Correlation with Gestational Age | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Establishment of Normal ADC Values and Morphological Parameters of the Fetal Kidney Using Magnetic Resonance Imaging and Analysis of their Correlation with Gestational Age Yangmei Pu, Shuzhen Ma, Qiyan Wang, Ran Li, Xuejing Zou, Yuchen Liu, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8288896/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 10 You are reading this latest preprint version Abstract Background Fetal renal developmental abnormalities are among the most common congenital malformations and are associated with adverse perinatal outcomes. However, existing fetal magnetic resonance imaging (MRI) studies are limited by small sample sizes and the lack of comprehensive gestational age (GA)–specific reference ranges that integrate both morphological and functional parameters. This study aimed to establish multiparametric MRI reference ranges for normal fetal kidneys and to characterize their relationships with GA. Methods In this retrospective single-center observational study, 313 singleton pregnancies (GA 23–39 weeks) with normal postnatal urinary outcomes underwent 1.5T fetal MRI, including T2-weighted and diffusion-weighted imaging sequences. Morphological parameters [anteroposterior, transverse and longitudinal diameters, and mean renal parenchymal thickness (MRPT)] and functional parameters [T2 relative signal intensity (RSI-T2) and apparent diffusion coefficient (ADC)] were measured for both kidneys. Reproducibility was assessed using intraclass correlation coefficients (ICC). Correlations between MRI parameters and GA were analyzed, and linear regression models were constructed for ADC. Results All morphological and functional parameters demonstrated good to excellent intra- and inter-observer reproducibility (ICC > 0.75). Renal diameters and MRPT increased significantly with GA (r = 0.72–0.89; all P < 0.0001), reflecting progressive macroscopic growth. In contrast, ADC values decreased moderately with advancing GA (right kidney: r = − 0.47; left kidney: r = − 0.52; both P < 0.0001), consistent with microstructural and functional maturation. The regression equations for ADC (×10⁻³ mm²/s) were: ADC_right = 3.23 − 0.049 × GA and ADC_left = 3.46 − 0.058 × GA. Conclusions This study provides GA-stratified reference ranges for key morphological and functional MRI parameters of normal fetal kidneys in the second and third trimesters. These quantitative benchmarks may improve prenatal assessment of fetal renal growth and maturation and support earlier detection and characterization of fetal renal developmental abnormalities. Trial registration Not applicable. fetal kidney magnetic resonance imaging diffusion-weighted imaging apparent diffusion coefficient gestational age renal development reference values prenatal diagnosis Figures Figure 1 Figure 2 Figure 3 Figure 4 Background Fetal renal developmental abnormalities represent one of the most common categories of congenital malformations, accounting for approximately 15%–20% of all fetal anomalies. Severe bilateral renal abnormalities in particular are strongly associated with oligohydramnios, pulmonary hypoplasia, and increased perinatal mortality, thereby contributing to adverse pregnancy outcomes and lifelong health implications [ 1 , 2 ] . Accurate prenatal evaluation of fetal renal morphology and function is therefore essential for determining the severity and type of abnormality, guiding perinatal management, informing prognosis, and supporting clinical decision-making. Ultrasound remains the first-line modality for prenatal screening owing to its accessibility, low cost, and non-invasiveness. However, its ability to assess fetal renal function is limited, and its diagnostic value is often compromised by maternal body habitus, fetal position, amniotic fluid volume, and operator-dependent variability [ 3 , 4 ] . In contrast, fetal magnetic resonance imaging (MRI) provides superior soft-tissue contrast and multiparametric functional assessment, increasingly demonstrating its complementary value in prenatal diagnosis. Among the available MRI biomarkers, the apparent diffusion coefficient (ADC) derived from diffusion-weighted imaging (DWI) quantitatively reflects the microscopic diffusion characteristics of water molecules within renal tissue, enabling indirect assessment of renal microstructure and functional maturation [ 5 , 6 ] . Previous studies have suggested that ADC values change with advancing gestational age and may serve as a quantitative marker of renal development [ 7 , 8 , 19 ] . For example, Savelli et al. reported a significant decline in fetal renal ADC values with increasing gestational age (ADC = 1.45 − 0.0104 × GA), whereas Manganaro et al. also demonstrated a decreasing trend (ADC = 1.69 − 0.0169 × GA; r = − 0.614). These findings consistently support the potential of ADC values as an imaging biomarker for monitoring fetal renal maturation. Despite these promising observations, the existing literature exhibits several limitations. Many studies include small sample sizes, resulting in insufficient statistical power to define robust gestational age–specific reference ranges. Most studies have focused solely on functional parameters such as ADC, without integrating complementary morphological markers (e.g., renal diameters and parenchymal thickness), thereby providing an incomplete representation of renal developmental status. Moreover, inconsistent criteria for defining “normal fetal kidneys” across studies further limit the reliability and clinical applicability of published reference values. To address these gaps, the present study aims to establish comprehensive multiparametric MRI reference ranges for normal fetal kidneys during the second and third trimesters, incorporating both morphological (renal size and parenchymal thickness) and functional (ADC and T2 relative signal intensity) indicators. By analyzing their correlations with gestational age, this study seeks to provide accurate, reproducible, and clinically meaningful imaging benchmarks for assessing fetal renal maturation, ultimately laying the groundwork for early detection and prognostic evaluation of fetal renal developmental abnormalities. Methods Study Design and Participants This retrospective, observational study was conducted at Sichuan Provincial Maternity and Child Health Care Hospital and was approved by the Medical Ethics Review Committee of Sichuan Provincial Maternity and Child Health Care Hospital (Approval No. 20240419-076). Written informed consent was obtained from all participants and/or their legal guardians prior to MRI examination. Pregnant women who underwent fetal MRI between June 2018 and June 2023 were screened for eligibility. Inclusion criteria were: (1) singleton pregnancy; (2) gestational age between 23 and 39 weeks confirmed by first‑trimester ultrasonography; (3) MRI images of sufficient diagnostic quality to allow quantitative analysis; (4) normal fetal renal morphology and signal characteristics confirmed independently by two radiologists with ≥10 years of fetal MRI experience; and (5) a normal neonatal urinary system confirmed through 12–18‑month postpartum follow-up. These follow-up findings constituted the reference standard for defining “normal fetal kidneys.” Exclusion criteria included: (1) maternal systemic diseases (e.g., gestational diabetes, hypertensive disorders of pregnancy, autoimmune or connective tissue disorders); (2) fetal anomalies affecting other organ systems or chromosomal abnormalities confirmed by prenatal or postnatal genetic testing; (3) severe MRI artifacts resulting from fetal motion or technical limitations that precluded reliable measurement; and (4) incomplete clinical data or loss to postpartum follow-up. MRI Acquisition Protocol All fetal MRI examinations were performed using a GE Signa HDXt 1.5T MRI system equipped with an 8-channel phased-array body coil. To ensure consistency and quantitative reliability, the MRI system underwent daily quality assurance calibration and scheduled phantom testing. The imaging protocol consisted of T2‑weighted single‑shot fast spin‑echo (SS‑FSE), Fiesta steady‑state sequences, T1‑weighted FSPGR, and diffusion‑weighted imaging (DWI) utilizing two b‑values (0 and 600 s/mm²). Total acquisition time ranged from approximately 12 to 17 minutes, with maternal positioning and sequence order optimized to minimize fetal motion.Detailed MRI acquisition parameters are summarized in Table 1. Sequence Technique Slice thickness/gap FOV (mm) TR (ms) TE (ms) Flip angle Matrix Plane T2WI SS-FSE (Single-shot fast spin echo) 3 / 0 380 × 380 1800 100 / 320 × 256 Coronal, sagittal, axial T2WI Fiesta (Fast imaging employing steady-state acquisition) 3 / 0 380 × 380 3.5 1.4 90 224 × 224 Coronal, sagittal, axial DWI DWI (Diffusion-weighted imaging, b =0,600 s/mm²) 4 / 0 380 × 380 4200 70 / 128×128 Coronal, axial T1WI FSPGR (Fast spoiled gradient echo) 4 / 1 380 × 380 155 min full 80 228 × 160 Coronal, axial Image Processing and Quantitative Measurement Image analysis was performed on an AW 4.7 workstation. Two radiologists with 8 and 10 years of fetal MRI experience independently reviewed all datasets while blinded to gestational age and clinical information. Prior to the study, both radiologists underwent standardized training on ROI placement to ensure methodological consistency. Functional parameters included:Apparent diffusion coefficient (ADC): Three circular ROIs (~15–20 mm²) were manually placed on ADC maps at the upper pole, renal hilum, and lower pole of each kidney, carefully avoiding renal sinus fat, collecting system, and peripheral susceptibility artifacts. Mean ADC was calculated from the three ROIs.T2 relative signal intensity (RSI‑T2): RSI‑T2 was computed as the ratio of renal parenchymal signal intensity to hepatic parenchymal signal intensity on axial T2WI obtained at comparable anatomical levels(RSI=SI_renal / SI_live). Morphological parameters included:Anteroposterior diameter (AD): measured on axial T2WI at the renal hilum level.Transverse diameter (TD) and longitudinal diameter (LD): measured on coronal T2WI slices demonstrating maximal renal extent.Mean renal parenchymal thickness (MRPT): calculated from measurements at the upper, mid, and lower poles. Each parameter was measured three times per kidney, and mean values were used for statistical analyses. To assess reproducibility, one radiologist repeated measurements on 30 randomly selected studies four weeks later. Intra-and inter-observer intraclass correlation coefficients (ICCs) were computed, with ICC > 0.75 considered indicative of good measurement reliability.Fetal renal T2-weighted images and ADC maps are shown in Figure 1(a–f). Statistical Analysis Statistical analyses were performed using SPSS version 26.0. Continuous variables were subjected to normality testing using the Shapiro–Wilk test. Normally distributed parameters were summarized using mean ± standard deviation and expressed with 95% reference intervals (x̄ ± 1.96s). For non-normally distributed data, percentile‑based (P2.5–P97.5) reference intervals were applied.Correlation between renal MRI parameters and gestational age was evaluated using Pearson correlation analysis for normally distributed variables and Spearman rank correlation for non-normal variables. Linear regression analyses were performed to model the relationship between ADC and gestational age, with assessment of fit and residual distribution. A two‑tailed P‑value < 0.05 was considered statistically significant.The detailed study design is presented in Figure 2. Results Characteristics of Study Population and Data Distribution A total of 313 fetuses with normal postnatal urinary outcomes were included in this study. The distribution of cases across gestational age (GA) groups is summarized in Tables 2 and 3. Maternal age ranged from 20 to 44 years (median: 28.7 years). Shapiro–Wilk testing showed that the morphological parameters—anteroposterior diameter (AD), transverse diameter (TD), longitudinal diameter (LD), and mean renal parenchymal thickness (MRPT)—followed a normal distribution (P > 0.05), whereas the apparent diffusion coefficient (ADC) and T2 relative signal intensity (RSI-T2) values showed non-normal distribution patterns (P < 0.05). Measurement Reliability High measurement reproducibility was demonstrated across all renal parameters. For morphological measures (AD, TD, LD, MRPT), both intra- and inter-observer ICCs exceeded 0.90, indicating excellent reliability. For functional measures, the inter-observer ICCs were 0.89 for ADC and 0.85 for RSI-T2, while the intra-observer ICCs were 0.92 and 0.88, respectively. Establishment of Normal Reference Ranges Reference ranges stratified by gestational week were generated in accordance with data distribution characteristics.Functional parameters: ADC and RSI-T2 values were expressed using percentile-based reference intervals (P2.5-P97.5) due to non-normal distribution (Table 2).Morphological parameters: AD, TD, LD, and MRPT values were normally distributed and therefore expressed as mean±1.96 SD (Table 3).Together, these ranges provide a comprehensive normative dataset for fetal renal morphology and function during the second and third trimesters. Table 2. Gestational age–stratified reference ranges (2.5th–97.5th percentiles) for combined right and left fetal renal functional MRI parameters. Gestational week number Right renal Left renal ADC (×10⁻³ mm²/s) RSI-T2 ADC (×10⁻³ mm²/s) RSI-T2 23 12 2.32-2.40 1.62-1.96 2.26-2.38 1.48-1.94 24 24 1.75-1.99 1.58-1.75 1.75-2.08 1.54-1.72 25 12 1.80-1.88 1.45-1.76 1.76-1.81 1.43-1.69 26 21 1.83-1.98 1.52-1.69 1.91-2.04 1.52-1.73 27 12 1.71-1.93 1.63-1.83 1.76-2.00 1.63-1.84 28 17 1.61-2.07 1.58-1.84 1.60-2.12 1.62-1.93 29 12 1.66-2.17 1.49-1.63 1.73-2.20 1.46-1.63 30 14 1.80-2.02 1.55-1.75 1.60-1.97 1.58-1.87 31 39 1.82-2.13 1.63-1.78 1.75-2.08 1.64-1.85 32 45 1.56-1.80 1.69-1.85 1.51-1.68 1.69-1.89 33 37 1.46-1.70 1.63-1.81 1.46-1.74 1.64-1.86 34 29 1.36-1.60 1.59-1.78 1.31-1.52 1.64-1.86 35 11 1.34-1.62 1.55-1.76 1.25-1.54 1.66-1.91 36 16 1.24-1.42 1.67-1.81 1.19-1.33 1.69-1.92 37 6 1.13-1.73 1.69-2.22 1.09-1.63 1.57-2.33 38 6 1.11-1.45 1.79-2.30 1.06-1.46 1.69-2.22 ADC（Mean apparent diffusion coefficient） = (upper renal pole + renal axis renal hilar level + renal lower pole) apparent diffusion coefficient / 3；RSI-T2（relative signal intensity on T2W）=(The T2-weighted imaging (T2WI) signal intensity of the renal parenchyma )/ the hepatic parenchyma. Table 3. Gestational age–stratified reference ranges (2.5th–97.5th percentiles) for morphological MRI parameters of the right and left fetal kidneys separately. Gestational week number Right renal Left renal LD (cm) TD (cm) AD (cm) MRPT (cm) LD (cm) TD (cm) AD (cm) MRPT (cm) 23 12 2.01-2.15 1.33-1.44 1.34-1.39 0.53-0.56 2.00-2.09 1.26-1.31 1.27-1.33 0.53-0.58 24 24 2.16-2.37 1.34-1.45 1.35-1.45 0.57-0.60 2.12-2.28 1.35-1.47 1.38-1.48 0.55-0.58 25 12 2.42-2.56 1.422-1.53 1.44-1.53 0.62-0.64 2.31-2.42 1.34-1.39 1.35-1.40 0.56-0.62 26 21 2.69-2.84 1.63-1.72 1.66-1.73 0.62-0.67 2.57-2.74 1.59-1.70 1.59-1.71 0.59-0.62 27 12 2.72-2.84 1.64-1.85 1.58-1.80 0.61-0.72 2.67-2.87 1.68-1.83 1.62-1.81 0.61-0.66 28 17 2.81-3.00 1.73-1.92 1.81-2.01 0.68-0.78 2.77-3.03 1.67-1.90 1.77-2.01 0.61-0.67 29 12 2.70-3.09 1.74-1.89 1.80-1.99 0.69-0.76 2.79-3.14 1.73-1.88 1.85-1.99 0.64-0.77 30 14 3.30-3.39 1.79-1.91 1.76-1.97 0.71-0.76 3.24-3.35 1.85-1.94 1.83-2.02 0.67-0.75 31 39 3.12-3.31 1.81-1.96 1.86-1.99 0.73-0.78 3.08-3.25 1.80-1.93 1.74-1.93 0.75-0.81 32 45 3.29-3.45 1.80-1.94 1.97-2.07 0.71-0.77 3.20-3.37 1.85-1.97 1.93-2.03 0.73-0.78 33 37 3.32-3.52 1.97-2.14 2.02-2.16 0.75-0.81 3.43-3.60 1.91-2.06 1.95-2.08 0.74-0.81 34 29 3.50-3.72 2.11-2.30 2.08-2.24 0.76-0.82 3.45-3.70 2.11-2.25 2.10-2.26 0.78-0.82 35 11 3.44-3.77 2.10-2.29 2.05-2.31 0.78-0.84 3.68-3.98 2.01-2.22 2.07-2.24 0.82-0.97 36 16 3.73-3.88 2.28-2.51 2.19-2.47 0.79-0.84 3.74-3.93 2.16-2.37 2.14-2.44 0.80-0.91 37 6 3.79-4.25 2.14-2.54 2.33-2.50 0.78-0.85 3.82-4.29 2.23-2.71 2.11-2.48 0.74-0.87 38 6 4.04-4.35 2.24-2.66 2.17-2.57 0.82-0.90 4.00-4.26 2.17-2.55 2.19-2.50 0.82-0.95 LD:longitudinal diameter(cm),TD:Transverse Diameter(cm),AD:Anteroposterior Diameter(cm),MRPT:Mean renal parenchymal thickness(cm).MRPT = (upper polar renal parenchymal thickness + renal hilar renal thickness + lower polar renal parenchymal thickness) . Correlation Between Renal Parameters and Gestational Age Spearman correlation analysis demonstrated a moderate negative correlation between ADC and gestational age for both kidneys (right: r = −0.46, P < 0.0001; left: r = −0.52, P < 0.0001). RSI-T2 values showed a very weak to weak positive correlation with gestational age (right: r = 0.148; left: r = 0.200; both P < 0.0001). In contrast, Pearson correlation analysis revealed strong positive correlations between all morphological indicators and gestational age (all P < 0.0001):LD: r = 0.88 (right), r = 0.89 (left);TD: r = 0.78 (right), r = 0.80 (left);AD: r = 0.81 (right), r = 0.78 (left);MRPT: r = 0.72 (right), r = 0.74 (left).Scatter plots illustrating these relationships are shown in Figure 3 and Figure 4. Regression Analysis Given the negative correlation between ADC and gestational age as well as the positive correlation between MRPT and gestational age, linear regression models were constructed to characterize ADC and MRPT developmental trajectories. Right kidney:ADC (×10⁻³ mm²/s) = 3.23 − 0.049 × GA (weeks)(R² = 0.218, P < 0.0001) Right kidney:MRPT(cm)=0.026× GA (weeks)-0.037(R² = 0.518, P < 0.0001) Left kidney:ADC (×10⁻³ mm²/s) = 3.46 − 0.058 × GA (weeks)(R² = 0.273, P < 0.0001) Left kidney:MRPT(cm)=0.025× GA (weeks)-0.027(R² = 0.548, P < 0.0001) These models quantify the progressive decreases in ADC values and thickening of MRPT with advancing gestational age, establish predictive equations for clinical use. Discussion In this study, we established comprehensive multiparametric MRI reference ranges for normal fetal kidneys during the second and third trimesters, integrating both morphological and functional indicators. Our findings demonstrate that renal morphological parameters—including LD, TD, AD, and MRPT—show strong positive correlations with gestational age, whereas ADC values exhibit a moderate but significant decline with advancing gestation. Together, these results not only reflect the coordinated growth and maturation of fetal renal structures but also highlight the complementary value of combining morphologic and diffusion-based functional markers in evaluating fetal renal development. Physiological Interpretation of Increasing Renal Parenchymal Thickness with Gestation Our results show a steady increase in MRPT from 23 to 38 weeks of gestation, with a strong correlation with GA (r > 0.72). This pattern is in line with the established trajectory of renal development. After approximately 20 weeks, nephrogenesis gradually transitions from formation of new nephrons to hypertrophic growth of existing glomeruli and tubules [ 9 , 12 ] . Although nephron number becomes largely fixed by 34–36 weeks, tubular length, branching complexity, interstitial tissue volume, and vascular development continue to increase [ 16 ] . These microstructural processes manifest as macroscopic thickening of the renal parenchyma, supporting MRPT as a reliable morphological indicator of renal maturation. Clinically, deviations from the gestational-age-specific MRPT reference range may serve as early warning signs of renal pathology. Reduced parenchymal thickness may indicate renal hypoplasia or congenital parenchymal disease, whereas compensatory hypertrophy secondary to obstructive uropathy or hereditary nephropathies may present as increased MRPT [ 10 , 13 ] . Thus, MRPT provides a readily interpretable morphological marker with high clinical relevance in prenatal diagnostics . Mechanisms Underlying the Decline in ADC Values With Advancing Gestation A notable finding of this study is the progressive decrease in renal ADC values with increasing gestational age, consistent with previous observations [ 7 , 8 , 19 ] . This trend can be attributed to several physiological mechanisms:①Increasing cellular density and structural complexity:As nephrons proliferate and tubular structures elongate and thicken, the extracellular diffusion space becomes progressively restricted. This microstructural “densification” reduces the free movement of water molecules, directly contributing to lower ADC values [ 8 , 15 ] .②Maturation of tubular transport function:During late gestation, the renal tubular epithelium undergoes functional maturation, leading to increasing reabsorption of water and solutes and the establishment of the corticomedullary osmotic gradient. Consequently, water molecules are increasingly compartmentalized within tubular and interstitial spaces, further restricting diffusivity [ 17 ] .③Changes in renal perfusion contribution:Although absolute renal blood flow increases with gestation, its proportion of fetal cardiac output remains comparatively low (2%–4%), substantially less than in neonates and adults. Thus, perfusion-related pseudodiffusion contributes minimally to the overall ADC signal during fetal life, reinforcing the dominant effect of structural restriction [ 18 ] . The stronger negative correlation observed in the left kidney compared with the right may reflect subtle anatomical or physiological differences, though further investigation is warranted to clarify this asymmetry. Integrated Diagnostic Value of Morphological and Functional MRI Parameters The combined analysis of structural and functional MRI parameters provides a more comprehensive assessment of fetal renal development. Morphological parameters, which increase linearly with gestational age, reflect macroscopic organ growth. In contrast, the decrease in ADC values captures microstructural maturation and functional development. The distinct but complementary patterns of change in these parameters underscore a morphology–function dissociation that may enhance diagnostic precision.For example:Early renal hypoplasia may present as reduced MRPT with abnormally elevated ADC, indicating impaired parenchymal development and increased diffusivity.Early obstructive nephropathy may initially exhibit decreased ADC values, reflecting cytotoxic edema or early microstructural alterations, before morphological enlargement becomes apparent.Thus, integrating MRPT and ADC values may enable earlier and more accurate identification of subtle renal abnormalities compared with using either metric alone. Study Limitations Several limitations should be acknowledged. First, although the total cohort size was relatively large, certain late-gestation strata (≥ 37 weeks) contained fewer cases, which may slightly limit the robustness of reference ranges for these gestational ages. Second, the study was conducted at a single tertiary center, introducing potential selection bias and limiting generalizability to broader populations. Third, although measurement reproducibility was high, ADC values remain inherently sensitive to factors such as ROI placement, fetal motion, and sequence-specific technical parameters. Despite standardized protocols and repeatability assessments, residual variability is unavoidable. Future multicenter and prospective studies are needed to validate these findings across different MRI platforms and populations. Conclusions This study established exploratory gestational age–specific reference ranges for key morphological and functional MRI parameters of normal fetal kidneys. Renal size and parenchymal thickness increase steadily with gestation, reflecting macroscopic organ growth and providing robust quantitative markers for assessing structural development, whereas ADC values decline as a result of microstructural and functional maturation. Together, these markers offer a robust quantitative framework for evaluating fetal renal development. Their combined application may substantially enhance the prenatal detection, characterization, and prognostic assessment of fetal renal anomalies. Future multicenter studies are required to further validate these reference intervals and further explore their diagnostic utility in fetal renal disorders. Abbreviations ADC apparent diffusion coefficient DWI diffusion-weighted imaging GA gestational age ICC intraclass correlation coefficient MRI magnetic resonance imaging MRPT mean renal parenchymal thickness ROI region of interest RSI-T2 T2 relative signal intensity T2WI T2-weighted imaging Declarations Ethics approval and consent to participate This retrospective observational study was conducted at Sichuan Provincial Maternity and Child Health Care Hospital and was approved by the Medical Ethics Review Committee of Sichuan Provincial Maternity and Child Health Care Hospital (Approval No. 20240419-076).All procedures involving human participants were performed in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Declaration of Helsinki and its later amendments. Written informed consent to participate was obtained from all pregnant women prior to fetal MRI examination. Consent for publication Written informed consent for publication of anonymized clinical data and imaging was obtained from all participants and/or their legal guardians. The publication of anonymized data derived from this study was approved by the Medical Ethics Review Committee of Sichuan Provincial Maternity and Child Health Care Hospital (Approval No. 20240419-076). Competing interests The authors declare that they have no competing interests. Authors’information Not applicable. Funding The authors received no specific funding for this work. Author Contribution YMP and MK conceived and designed the study and supervised the overall project. YMP, QYW, RL, and XJZ performed case selection, image review, data collection, and image and statistical analysis. SZM, as the radiologic technologist, conducted and coordinated the fetal MRI examinations and ensured image quality. YCL, as a research scientist from GE Healthcare, provided technical support for MRI sequence optimization and quantitative parameter implementation. YMP drafted the manuscript. All authors critically revised the manuscript for important intellectual content, approved the final version, and agreed to be accountable for all aspects of the work. Acknowledgement The authors would like to express their sincere gratitude to all patients and their families for their willingness to participate in this study and for their cooperation throughout the research period. The authors also thank the leadership and colleagues of the Department of Radiology, Sichuan Provincial Maternity and Child Health Care Hospital, for their continuous support. The approval and oversight provided by the Medical Ethics Committee of Sichuan Provincial Maternity and Child Health Care Hospital are gratefully acknowledged. Data Availability The datasets that support the findings of this study are available from the corresponding author on reasonable request. References Hill BJ, Joe BN, Qayyum A, et al. Supplemental value of MRI in fetal abdominal disease detected on prenatal sonography: preliminary experience.AJR. Am J Roentgenol. 2005;184(3):993–8. Cassart M, Massez A, Metens T, et al. Complementary role of MRI after sonography in assessing bilateral urinary tract anomalies in the fetus.AJR Am. J Roentgenol. 2004;182(3):689–95. Vermoolen MA, Kwee TC, Nievelstein RA. Apparent diffusion coefficient measurements in the differentiation between benign and malignant lesions: a systematic review. Insights Imaging. 2012;3(4):395–409. Colagrande S, Carbone SF, Carusi LM, Cova M, Villari N. Magnetic resonance diffusion-weighted imaging: extraneurological applications. Radiol Med. 2006;111(3):392–419. English, Italian. Prasad PV, Priatna A. Functional imaging of the kidneys with fast MRI techniques. Eur J Radiol. 1999;29(2):133–48. Thoeny HC, De Keyzer F. Extracranial applications of diffusion-weighted magnetic resonance imaging. Eur Radiol. 2007;17(6):1385–93. Al Salmi I, Al Hajriy M, Hannawi SU. Measurement and Kidney Development: a Mini-Review for Nephrologists.Saudi. J Kidney Dis Transpl 2021 Jan-Feb;32(1):174–82. Manganaro L, Francioso A, Savelli S, Tomei A, Fierro F, Di Maurizio M, Coratella F, Perrone A, Ballesio L, Giancotti A, Porfiri L, Marini M. Fetal MRI with diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) assessment in the evaluation of renal development: preliminary experience in normal kidneys. Radiol Med. 2009;114(3):403–13. Dos Santos Junior AC, de Miranda DM, Simões e Silva AC. Congenital anomalies of the kidney and urinary tract: an embryogenetic review. Birth Defects Res C Embryo Today. 2014;102(4):374–81. 10.1002/bdrc.21084 . Wynyard P, Chitty LS. Dysplastic kidneys. Semin Fetal Neonat al Med. 2008;13:142–51. Woolf AS. A molecular and genetic view of human renal and urinary tract malformations. Kidney Int. 2000;58:500–12. Sadler TW. The urogenital system. In: Sadler TW, editor. Langman’s Medical Embry ology. 9th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2004. pp. 321–62. Cuckow PM, Nyirady P, Winyard PJD. Normal and abnormal development of the urogenital tract. Prenat Diagn. 2001;21:908–16. Faghihimehr A, Gharavi M, Mancuso M, Sreedher G. Fetal MR imaging in urogenital system anomalies. J Matern Fetal Neonatal Med. 2019;32(20):3487–94. Gubhaju L, Black MJ. The baboon as a good model for studies of human kidney development. Pediatr Res. 2005;58(3):505–9. 10.1203/01.PDR.0000179397.20862.73 . Almeida JR, Mandarim-de-Lacerda CA. Quantitative study of the comma-shaped body, S-shaped body and vascularized glomerulus in the second and third human gestational trimesters. Early Hum Dev. 2002;69(1–2):1–13. Laissy JP, Idée JM, Fernandez P, Floquet M, Vrtovsnik F, Schouman-Claeys E. Magnetic resonance imaging in acute and chronic kidney diseases: present status. Nephron Clin Pract. 2006;103(2):c50–7. 10.1159/000090609 . Obara M, Kwon J, Yoneyama M, Ueda Y, Cauteren MV. Technical Advancements in Abdominal Diffusion-weighted Imaging. Magn Reson Med Sci. 2023;22(2):191–208. 10.2463/mrms.rev.2022-0107 . Savelli S, Di Maurizio M, Perrone A et al. MRI with diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) assessment in the evaluation of normal and abnormal fetal kidneys: Preliminary experience. Prenat Diagn, 27(12), 1104–11. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 02 Mar, 2026 Reviews received at journal 20 Feb, 2026 Reviewers agreed at journal 19 Jan, 2026 Reviews received at journal 13 Jan, 2026 Reviewers agreed at journal 07 Jan, 2026 Reviewers invited by journal 07 Jan, 2026 Editor assigned by journal 05 Jan, 2026 Editor invited by journal 17 Dec, 2025 Submission checks completed at journal 17 Dec, 2025 First submitted to journal 17 Dec, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8288896","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":572332746,"identity":"586b7272-aa4a-4157-b5bb-22789808e560","order_by":0,"name":"Yangmei Pu","email":"","orcid":"","institution":"Sichuan Provincial Maternity and Child Health Care Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yangmei","middleName":"","lastName":"Pu","suffix":""},{"id":572332748,"identity":"f98f4eb7-a731-4975-adb8-6cea8fe401e9","order_by":1,"name":"Shuzhen Ma","email":"","orcid":"","institution":"Sichuan Provincial Maternity and Child Health Care Hospital","correspondingAuthor":false,"prefix":"","firstName":"Shuzhen","middleName":"","lastName":"Ma","suffix":""},{"id":572332749,"identity":"7e672a01-618a-496e-ad17-cd70395b2a42","order_by":2,"name":"Qiyan Wang","email":"","orcid":"","institution":"Sichuan Provincial Maternity and Child Health Care Hospital","correspondingAuthor":false,"prefix":"","firstName":"Qiyan","middleName":"","lastName":"Wang","suffix":""},{"id":572332750,"identity":"92c3c6e2-1f7b-49f9-aa97-bee9f4ef6230","order_by":3,"name":"Ran Li","email":"","orcid":"","institution":"Sichuan Provincial Maternity and Child Health Care Hospital","correspondingAuthor":false,"prefix":"","firstName":"Ran","middleName":"","lastName":"Li","suffix":""},{"id":572332751,"identity":"6c4ef29a-8c2e-4999-8706-0786cd856f8b","order_by":4,"name":"Xuejing Zou","email":"","orcid":"","institution":"Sichuan Provincial Maternity and Child Health Care Hospital","correspondingAuthor":false,"prefix":"","firstName":"Xuejing","middleName":"","lastName":"Zou","suffix":""},{"id":572332752,"identity":"0d7b4487-0113-4708-bf99-c03fc3200021","order_by":5,"name":"Yuchen Liu","email":"","orcid":"","institution":"MR Research, GE Healthcare","correspondingAuthor":false,"prefix":"","firstName":"Yuchen","middleName":"","lastName":"Liu","suffix":""},{"id":572332753,"identity":"9455c911-fe62-4e89-993c-01412177c9fd","order_by":6,"name":"Min Kang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAz0lEQVRIie3RMQrCMBTG8UDgdUnr+kBITyCkBApdPEtC1+oiSMdCIZMHcOgthM6ZnIqzoyI4dVBcBXXUqXETzH//wft4hPh8PxjQ0e1wKR8cKLVuJAqqNFl3VEaBUW6EMyvGoaGas044HoZKidCAAiyu+55M+aQaJvaAOzYHnG2yhuQytYNEV0IscfEi7ZgRq9thkhNUILTB4uxI2JagNUob1oEjCVaQVJ2VEBiZNcJhS1wzerqXlsc1Pe77csoHyUfIHF/zTr4VPp/P9xc9ATlCPRqOpnWQAAAAAElFTkSuQmCC","orcid":"","institution":"Sichuan Provincial Maternity and Child Health Care Hospital","correspondingAuthor":true,"prefix":"","firstName":"Min","middleName":"","lastName":"Kang","suffix":""}],"badges":[],"createdAt":"2025-12-05 15:08:17","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8288896/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8288896/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":100022888,"identity":"9fcf5b99-4d4c-4edd-9496-acff84662234","added_by":"auto","created_at":"2026-01-12 08:10:33","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1718958,"visible":true,"origin":"","legend":"","description":"","filename":"EstablishmentofNormalADCValuesandMorphologic2025.12.17.docx","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/29abea60e268a24d836907db.docx"},{"id":100022876,"identity":"6d35a727-ef70-4bc5-90c1-255c497cd98c","added_by":"auto","created_at":"2026-01-12 08:10:31","extension":"json","order_by":1,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":9702,"visible":true,"origin":"","legend":"","description":"","filename":"fc9ac69b24c744efa44af7e4ca207659.json","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/746c201f1eeefc9729be4153.json"},{"id":100022901,"identity":"b19d0149-953f-4664-8449-d940462b38b2","added_by":"auto","created_at":"2026-01-12 08:10:39","extension":"xml","order_by":2,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":94156,"visible":true,"origin":"","legend":"","description":"","filename":"fc9ac69b24c744efa44af7e4ca2076591enriched.xml","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/56d119e8e8fc675ffe135b00.xml"},{"id":100022882,"identity":"3115986a-705e-44de-9b66-5ac141c0bb54","added_by":"auto","created_at":"2026-01-12 08:10:32","extension":"jpeg","order_by":5,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":647139,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/e168e8bd2f3bee7f677e1dc8.jpeg"},{"id":100022864,"identity":"c1a99369-d0c8-44d3-a03f-2fc2bf192bf0","added_by":"auto","created_at":"2026-01-12 08:10:28","extension":"jpeg","order_by":6,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":402444,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/7a375b72edf0c95cb126c5d9.jpeg"},{"id":100022904,"identity":"b99eceae-af73-4c68-abe6-520bf68f7e6f","added_by":"auto","created_at":"2026-01-12 08:10:40","extension":"jpeg","order_by":7,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":312013,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/183a3054a329f8c5095e0fc7.jpeg"},{"id":100362600,"identity":"efbb3449-c26f-4914-a89a-6f122264599d","added_by":"auto","created_at":"2026-01-16 07:47:24","extension":"jpeg","order_by":8,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":175058,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/6cf25100dd834ddf89e25076.jpeg"},{"id":100362953,"identity":"b1a84415-0f73-4c8f-8864-2df19a1c837e","added_by":"auto","created_at":"2026-01-16 07:48:23","extension":"jpeg","order_by":9,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":75791,"visible":true,"origin":"","legend":"","description":"","filename":"groupimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/44815ddf547644b400459b9f.jpeg"},{"id":100022886,"identity":"d25b7320-57cc-4ac7-b47a-287b82ff7fce","added_by":"auto","created_at":"2026-01-12 08:10:32","extension":"jpeg","order_by":10,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":87110,"visible":true,"origin":"","legend":"","description":"","filename":"groupimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/3e1c7898b6fdfba530f01aa3.jpeg"},{"id":100022953,"identity":"841eb3dd-6527-42c8-beea-54f388531007","added_by":"auto","created_at":"2026-01-12 08:10:44","extension":"jpeg","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":60751,"visible":true,"origin":"","legend":"","description":"","filename":"groupimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/35958e1f15b03fa60433bc43.jpeg"},{"id":100022892,"identity":"76db649b-e1c7-4a77-a4e3-3ab38f2263b2","added_by":"auto","created_at":"2026-01-12 08:10:33","extension":"wmf","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":2154,"visible":true,"origin":"","legend":"","description":"","filename":"image10.wmf","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/0c63ccb5f8ca458eb30611a2.wmf"},{"id":100022883,"identity":"f9012fbe-16d0-4d56-8906-3e9b65da4ae1","added_by":"auto","created_at":"2026-01-12 08:10:32","extension":"wmf","order_by":13,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":2154,"visible":true,"origin":"","legend":"","description":"","filename":"image11.wmf","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/ef9d1cd353081eaa10b36564.wmf"},{"id":100022880,"identity":"18ca0c9c-ba18-4a2e-af45-f67de4fa87ff","added_by":"auto","created_at":"2026-01-12 08:10:32","extension":"wmf","order_by":14,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":2154,"visible":true,"origin":"","legend":"","description":"","filename":"image12.wmf","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/09b5b558db236e43bbf3de65.wmf"},{"id":100022877,"identity":"cc2f64a6-2e6f-404c-9118-3d408136f0af","added_by":"auto","created_at":"2026-01-12 08:10:32","extension":"wmf","order_by":15,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":2154,"visible":true,"origin":"","legend":"","description":"","filename":"image13.wmf","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/ee8e7ee7199a70c46a301b7b.wmf"},{"id":100022863,"identity":"9e2a7dc4-1a11-4ff7-90a5-e09c1f715e94","added_by":"auto","created_at":"2026-01-12 08:10:28","extension":"wmf","order_by":16,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":2154,"visible":true,"origin":"","legend":"","description":"","filename":"image8.wmf","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/0beec22b3785f1c25b409037.wmf"},{"id":100022897,"identity":"2b818190-5c14-4327-9b94-0b63ef5988e4","added_by":"auto","created_at":"2026-01-12 08:10:39","extension":"wmf","order_by":17,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":2154,"visible":true,"origin":"","legend":"","description":"","filename":"image9.wmf","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/ebb1805674930bdbab6ed07c.wmf"},{"id":100022873,"identity":"ba71ee91-224d-40fd-b7a1-d8cec152e55b","added_by":"auto","created_at":"2026-01-12 08:10:31","extension":"png","order_by":18,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":119254,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/0bc68cd2bca1d626e480262e.png"},{"id":100022870,"identity":"67b44c07-d987-4852-bdbb-d46e48d93720","added_by":"auto","created_at":"2026-01-12 08:10:30","extension":"png","order_by":19,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":82418,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/feca5af2df237f1685318e8c.png"},{"id":100362634,"identity":"4761c1fd-0471-4299-bd6d-57b9629c71ae","added_by":"auto","created_at":"2026-01-16 07:47:47","extension":"png","order_by":20,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":63708,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/a5fc50299731617e506154f2.png"},{"id":100022900,"identity":"46bfab20-f601-4099-901b-4ef396f19846","added_by":"auto","created_at":"2026-01-12 08:10:39","extension":"png","order_by":21,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":32708,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/37043327d9e8fb1b40fe792d.png"},{"id":100022878,"identity":"c6d5ce5b-bfec-41b5-867a-9deaf5c97cc8","added_by":"auto","created_at":"2026-01-12 08:10:32","extension":"png","order_by":22,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":44873,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinegroupimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/1707b0323e169b97b781df37.png"},{"id":100022895,"identity":"c8ad474c-7bec-47eb-a532-a09f4b8ddacc","added_by":"auto","created_at":"2026-01-12 08:10:33","extension":"png","order_by":23,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":50783,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinegroupimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/9179e5cf30d2d9d42c1ddafe.png"},{"id":100022887,"identity":"a90b0e0b-0df8-4022-83cb-f93ec8b78e77","added_by":"auto","created_at":"2026-01-12 08:10:33","extension":"png","order_by":24,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":36810,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinegroupimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/5ac529ac69ac8f3570a6acb2.png"},{"id":100022869,"identity":"25c97a95-892b-4476-a7f9-e04b4d40ba14","added_by":"auto","created_at":"2026-01-12 08:10:30","extension":"png","order_by":25,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":409,"visible":true,"origin":"","legend":"","description":"","filename":"Onlineimage10.png","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/21b475002709ffde7090f800.png"},{"id":100022905,"identity":"807c0231-22a0-4a94-9a04-8fd33fa5c8d9","added_by":"auto","created_at":"2026-01-12 08:10:40","extension":"png","order_by":26,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":434,"visible":true,"origin":"","legend":"","description":"","filename":"Onlineimage11.png","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/3d2cb9327f3a449af6b41e49.png"},{"id":100022874,"identity":"321a3977-e207-43c4-ada5-bd9a1dbee3e5","added_by":"auto","created_at":"2026-01-12 08:10:31","extension":"png","order_by":27,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":440,"visible":true,"origin":"","legend":"","description":"","filename":"Onlineimage12.png","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/f3e8fb28364bc1150e51e334.png"},{"id":100022907,"identity":"1075bcc9-cab9-4511-83fb-3ba02bfeea9f","added_by":"auto","created_at":"2026-01-12 08:10:40","extension":"png","order_by":28,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":366,"visible":true,"origin":"","legend":"","description":"","filename":"Onlineimage13.png","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/afedf55d8190323cb93c15cb.png"},{"id":100362590,"identity":"2fc93093-b19d-40fb-9d9c-5c058446ad1d","added_by":"auto","created_at":"2026-01-16 07:47:23","extension":"png","order_by":29,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":424,"visible":true,"origin":"","legend":"","description":"","filename":"Onlineimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/d0f835f620471067fd461b1a.png"},{"id":100022875,"identity":"06070cc8-c420-46fa-97bc-6c18dd3aa0fe","added_by":"auto","created_at":"2026-01-12 08:10:31","extension":"png","order_by":30,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":441,"visible":true,"origin":"","legend":"","description":"","filename":"Onlineimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/5ae18ec961ed91ee98f04194.png"},{"id":100022866,"identity":"6952d7af-9ada-4c51-846f-e5a27103117e","added_by":"auto","created_at":"2026-01-12 08:10:29","extension":"xml","order_by":31,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":91399,"visible":true,"origin":"","legend":"","description":"","filename":"fc9ac69b24c744efa44af7e4ca2076591structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/df5c6503ebefa8d4d9bbdca1.xml"},{"id":100022902,"identity":"5c2c1cd3-520b-4581-80c5-98deab64e010","added_by":"auto","created_at":"2026-01-12 08:10:39","extension":"html","order_by":32,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":101350,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/634a971bf5697bee8aef6ca5.html"},{"id":100022867,"identity":"d678654b-c3b1-46b7-8fb7-d37fc99066c1","added_by":"auto","created_at":"2026-01-12 08:10:29","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":175328,"visible":true,"origin":"","legend":"\u003cp\u003eFetal renal at 31 weeks. (a–c) Transverse images: T2-weighted imaging (T2WI, a), diffusion-weighted imaging (DWI, b), and apparent diffusion coefficient (ADC) map (c). (d–f) Coronal images: T2WI (d), DWI (e), and ADC map (f).\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/47d88d662e5b109d825d8cdb.jpg"},{"id":100022865,"identity":"08326bfb-1448-4bef-ac95-8c5fe702fe87","added_by":"auto","created_at":"2026-01-12 08:10:29","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":105622,"visible":true,"origin":"","legend":"\u003cp\u003eThe technical flowchart of this study\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/8fbb74e1301fba502d212e22.jpg"},{"id":100362564,"identity":"cc5c3402-4fc7-4c54-963b-b4dcc31aed31","added_by":"auto","created_at":"2026-01-16 07:47:02","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":120709,"visible":true,"origin":"","legend":"\u003cp\u003eScatterplots with fitted regression lines showing the relationships between gestational age and renal morphological parameters. Panels (a–c) show the anteroposterior, transverse, and longitudinal diameters of the right kidney, and panels (d–f) show the corresponding parameters of the left kidney.\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/4b0596761504dd3dd3abdec4.jpg"},{"id":100022868,"identity":"0c21b8b4-29e2-49e2-9b95-9e72e695a2d4","added_by":"auto","created_at":"2026-01-12 08:10:29","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":89018,"visible":true,"origin":"","legend":"\u003cp\u003eScatterplots with fitted regression lines showing the relationships between gestational age and functional MRI parameters of the fetal kidneys. Panels (a–c) show mean renal parenchymal thickness (MRPT), T2 relative signal intensity (RSI-T2), and apparent diffusion coefficient (ADC) of the right kidney, and panels (d–f) show the corresponding parameters of the left kidney.\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/2624558d4dcaed6b5499c22f.jpg"},{"id":100381008,"identity":"e1d1726c-508e-429a-894a-66c28f6bd88b","added_by":"auto","created_at":"2026-01-16 10:36:57","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1476956,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8288896/v1/61e029fd-285a-417b-a5f7-26b9c5ace2d1.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Establishment of Normal ADC Values and Morphological Parameters of the Fetal Kidney Using Magnetic Resonance Imaging and Analysis of their Correlation with Gestational Age","fulltext":[{"header":"Background","content":"\u003cp\u003eFetal renal developmental abnormalities represent one of the most common categories of congenital malformations, accounting for approximately 15%\u0026ndash;20% of all fetal anomalies. Severe bilateral renal abnormalities in particular are strongly associated with oligohydramnios, pulmonary hypoplasia, and increased perinatal mortality, thereby contributing to adverse pregnancy outcomes and lifelong health implications \u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e. Accurate prenatal evaluation of fetal renal morphology and function is therefore essential for determining the severity and type of abnormality, guiding perinatal management, informing prognosis, and supporting clinical decision-making.\u003c/p\u003e \u003cp\u003eUltrasound remains the first-line modality for prenatal screening owing to its accessibility, low cost, and non-invasiveness. However, its ability to assess fetal renal function is limited, and its diagnostic value is often compromised by maternal body habitus, fetal position, amniotic fluid volume, and operator-dependent variability \u003csup\u003e[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e. In contrast, fetal magnetic resonance imaging (MRI) provides superior soft-tissue contrast and multiparametric functional assessment, increasingly demonstrating its complementary value in prenatal diagnosis. Among the available MRI biomarkers, the apparent diffusion coefficient (ADC) derived from diffusion-weighted imaging (DWI) quantitatively reflects the microscopic diffusion characteristics of water molecules within renal tissue, enabling indirect assessment of renal microstructure and functional maturation \u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e. Previous studies have suggested that ADC values change with advancing gestational age and may serve as a quantitative marker of renal development \u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e. For example, Savelli et al. reported a significant decline in fetal renal ADC values with increasing gestational age (ADC\u0026thinsp;=\u0026thinsp;1.45\u0026thinsp;\u0026minus;\u0026thinsp;0.0104 \u0026times; GA), whereas Manganaro et al. also demonstrated a decreasing trend (ADC\u0026thinsp;=\u0026thinsp;1.69\u0026thinsp;\u0026minus;\u0026thinsp;0.0169 \u0026times; GA; r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.614). These findings consistently support the potential of ADC values as an imaging biomarker for monitoring fetal renal maturation.\u003c/p\u003e\u003cp\u003eDespite these promising observations, the existing literature exhibits several limitations. Many studies include small sample sizes, resulting in insufficient statistical power to define robust gestational age\u0026ndash;specific reference ranges. Most studies have focused solely on functional parameters such as ADC, without integrating complementary morphological markers (e.g., renal diameters and parenchymal thickness), thereby providing an incomplete representation of renal developmental status. Moreover, inconsistent criteria for defining \u0026ldquo;normal fetal kidneys\u0026rdquo; across studies further limit the reliability and clinical applicability of published reference values.\u003c/p\u003e \u003cp\u003eTo address these gaps, the present study aims to establish comprehensive multiparametric MRI reference ranges for normal fetal kidneys during the second and third trimesters, incorporating both morphological (renal size and parenchymal thickness) and functional (ADC and T2 relative signal intensity) indicators. By analyzing their correlations with gestational age, this study seeks to provide accurate, reproducible, and clinically meaningful imaging benchmarks for assessing fetal renal maturation, ultimately laying the groundwork for early detection and prognostic evaluation of fetal renal developmental abnormalities.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cstrong\u003eStudy Design and Participants\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis retrospective, observational study was conducted at Sichuan Provincial Maternity and Child Health Care Hospital and was approved by the Medical Ethics Review Committee of Sichuan Provincial Maternity and Child Health Care Hospital (Approval No. 20240419-076). Written informed consent was obtained from all participants and/or their legal guardians prior to MRI examination. Pregnant women who underwent fetal MRI between June 2018 and June 2023 were screened for eligibility.\u003c/p\u003e\n\u003cp\u003eInclusion criteria were: (1) singleton pregnancy; (2) gestational age between 23 and 39 weeks confirmed by first‑trimester ultrasonography; (3) MRI images of sufficient diagnostic quality to allow quantitative analysis; (4) normal fetal renal morphology and signal characteristics confirmed independently by two radiologists with\u0026nbsp;\u0026ge;10 years of fetal MRI experience; and (5) a normal neonatal urinary system confirmed through 12\u0026ndash;18‑month postpartum follow-up. These follow-up findings constituted the reference standard for defining\u0026nbsp;\u0026ldquo;normal fetal kidneys.\u0026rdquo;\u003c/p\u003e\n\u003cp\u003eExclusion criteria included: (1) maternal systemic diseases (e.g., gestational diabetes, hypertensive disorders of pregnancy, autoimmune or connective tissue disorders); (2) fetal anomalies affecting other organ systems or chromosomal abnormalities confirmed by prenatal or postnatal genetic testing; (3) severe MRI artifacts resulting from fetal motion or technical limitations that precluded reliable measurement; and (4) incomplete clinical data or loss to postpartum follow-up.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMRI Acquisition Protocol\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll fetal MRI examinations were performed using a GE Signa HDXt 1.5T MRI system equipped with an 8-channel phased-array body coil. To ensure consistency and quantitative reliability, the MRI system underwent daily quality assurance calibration and scheduled phantom testing. The imaging protocol consisted of T2‑weighted single‑shot fast spin‑echo (SS‑FSE), Fiesta steady‑state sequences, T1‑weighted FSPGR, and diffusion‑weighted imaging (DWI) utilizing two b‑values (0 and 600 s/mm\u0026sup2;). Total acquisition time ranged from approximately 12 to 17 minutes, with maternal positioning and sequence order optimized to minimize fetal motion.Detailed MRI acquisition parameters are summarized in Table 1.\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" align=\"\" width=\"117%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSequence\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eTechnique\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSlice thickness/gap\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eFOV (mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eTR (ms)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eTE (ms)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eFlip angle\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eMatrix\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ePlane\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eT2WI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSS-FSE (Single-shot fast spin echo)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3 / 0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e380 \u0026times; 380\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1800\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e320 \u0026times; 256\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;Coronal, sagittal, axial\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eT2WI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;Fiesta (Fast imaging employing steady-state acquisition)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3 / 0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e380 \u0026times; 380\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e224 \u0026times; 224\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eCoronal, sagittal, axial\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eDWI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;DWI (Diffusion-weighted imaging, b =0,600 s/mm\u0026sup2;)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e4 / 0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e380 \u0026times; 380\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e4200\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e128\u0026times;128\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eCoronal, axial\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eT1WI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eFSPGR (Fast spoiled gradient echo)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e4 / 1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e380 \u0026times; 380\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e155\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003emin full\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e228 \u0026times; 160\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eCoronal, axial\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eImage Processing and Quantitative Measurement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eImage analysis was performed on an AW 4.7 workstation. Two radiologists with 8 and 10 years of fetal MRI experience independently reviewed all datasets while blinded to gestational age and clinical information. Prior to the study, both radiologists underwent standardized training on ROI placement to ensure methodological consistency.\u003c/p\u003e\n\u003cp\u003eFunctional parameters included:Apparent diffusion coefficient (ADC): Three circular ROIs (~15\u0026ndash;20 mm\u0026sup2;) were manually placed on ADC maps at the upper pole, renal hilum, and lower pole of each kidney, carefully avoiding renal sinus fat, collecting system, and peripheral susceptibility artifacts. Mean ADC was calculated from the three ROIs.T2 relative signal intensity (RSI‑T2): RSI‑T2 was computed as the ratio of renal parenchymal signal intensity to hepatic parenchymal signal intensity on axial T2WI obtained at comparable anatomical levels(RSI=SI_renal / SI_live).\u003c/p\u003e\n\u003cp\u003eMorphological parameters included:Anteroposterior diameter (AD): measured on axial T2WI at the renal hilum level.Transverse diameter (TD) and longitudinal diameter (LD): measured on coronal T2WI slices demonstrating maximal renal extent.Mean renal parenchymal thickness (MRPT): calculated from measurements at the upper, mid, and lower poles.\u003c/p\u003e\n\u003cp\u003eEach parameter was measured three times per kidney, and mean values were used for statistical analyses. To assess reproducibility, one radiologist repeated measurements on 30 randomly selected studies four weeks later. Intra-and inter-observer intraclass correlation coefficients (ICCs) were computed, with ICC \u0026gt; 0.75 considered indicative of good measurement reliability.Fetal renal T2-weighted images and ADC maps are shown in Figure 1(a\u0026ndash;f).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatistical Analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eStatistical analyses were performed using SPSS version 26.0. Continuous variables were subjected to normality testing using the Shapiro\u0026ndash;Wilk test. Normally distributed parameters were summarized using mean \u0026plusmn; standard deviation and expressed with 95% reference intervals (x̄ \u0026plusmn; 1.96s). For non-normally distributed data, percentile‑based (P2.5\u0026ndash;P97.5) reference intervals were applied.Correlation between renal MRI parameters and gestational age was evaluated using Pearson correlation analysis for normally distributed variables and Spearman rank correlation for non-normal variables. Linear regression analyses were performed to model the relationship between ADC and gestational age, with assessment of fit and residual distribution. A two‑tailed P‑value \u0026lt; 0.05 was considered statistically significant.The detailed study design is presented in Figure 2.\u003c/p\u003e"},{"header":"Results","content":"\u003ch3\u003eCharacteristics of Study Population and Data Distribution\u003c/h3\u003e\n\u003cp\u003eA total of 313 fetuses with normal postnatal urinary outcomes were included in this study. The distribution of cases across gestational age (GA) groups is summarized in Tables 2 and 3. Maternal age ranged from 20 to 44 years (median: 28.7 years). Shapiro\u0026ndash;Wilk testing showed that the morphological parameters\u0026mdash;anteroposterior diameter (AD), transverse diameter (TD), longitudinal diameter (LD), and mean renal parenchymal thickness (MRPT)\u0026mdash;followed a normal distribution (P \u0026gt; 0.05), whereas the apparent diffusion coefficient (ADC) and T2 relative signal intensity (RSI-T2) values showed non-normal distribution patterns (P \u0026lt; 0.05).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMeasurement Reliability\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;High measurement reproducibility was demonstrated across all renal parameters. For morphological measures (AD, TD, LD, MRPT), both intra- and inter-observer ICCs exceeded 0.90, indicating excellent reliability. For functional measures, the inter-observer ICCs were 0.89 for ADC and 0.85 for RSI-T2, while the intra-observer ICCs were 0.92 and 0.88, respectively.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEstablishment of Normal Reference Ranges\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eReference ranges stratified by gestational week were generated in accordance with data distribution characteristics.Functional parameters: ADC and RSI-T2 values were expressed using percentile-based reference intervals (P2.5-P97.5) due to non-normal distribution (Table 2).Morphological parameters: AD, TD, LD, and MRPT values were normally distributed and therefore expressed as mean\u0026plusmn;1.96 SD (Table 3).Together, these ranges provide a comprehensive normative dataset for fetal renal morphology and function during the second and third trimesters.\u003c/p\u003e\n\u003cp\u003eTable 2. Gestational age\u0026ndash;stratified reference ranges (2.5th\u0026ndash;97.5th percentiles) for combined right and left fetal renal functional MRI parameters.\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" align=\"\" width=\"112%\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\"\u003e\n \u003cp\u003e\u003cstrong\u003eGestational week\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\"\u003e\n \u003cp\u003e\u003cstrong\u003enumber\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\"\u003e\n \u003cp\u003e\u003cstrong\u003eRight \u0026nbsp;renal\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\"\u003e\n \u003cp\u003e\u003cstrong\u003eLeft \u0026nbsp;renal\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e\u003cstrong\u003eADC (\u0026times;10⁻\u0026sup3; mm\u0026sup2;/s)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u003cstrong\u003eRSI-T2\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u003cstrong\u003eADC (\u0026times;10⁻\u0026sup3; mm\u0026sup2;/s)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u003cstrong\u003eRSI-T2\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.32-2.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.62-1.96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.26-2.38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.48-1.94\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.75-1.99\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.58-1.75\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.75-2.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.54-1.72\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.80-1.88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.45-1.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.76-1.81\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.43-1.69\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.83-1.98\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.52-1.69\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.91-2.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.52-1.73\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.71-1.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.63-1.83\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.76-2.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.63-1.84\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.61-2.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.58-1.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.60-2.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.62-1.93\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.66-2.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.49-1.63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.73-2.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.46-1.63\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.80-2.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.55-1.75\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.60-1.97\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.58-1.87\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.82-2.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.63-1.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.75-2.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.64-1.85\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.56-1.80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.69-1.85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.51-1.68\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.69-1.89\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.46-1.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.63-1.81\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.46-1.74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.64-1.86\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.36-1.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.59-1.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.31-1.52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.64-1.86\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.34-1.62\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.55-1.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.25-1.54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.66-1.91\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.24-1.42\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.67-1.81\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.19-1.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.69-1.92\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.13-1.73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.69-2.22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.09-1.63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.57-2.33\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.11-1.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.79-2.30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.06-1.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.69-2.22\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eADC（Mean apparent diffusion coefficient） = (upper renal pole + renal axis renal hilar level + renal lower pole) apparent diffusion coefficient / 3；RSI-T2（relative signal intensity on T2W）=(The T2-weighted imaging (T2WI) signal intensity of the renal parenchyma )/ the hepatic parenchyma.\u003c/p\u003e\n\u003cp\u003eTable 3. Gestational age\u0026ndash;stratified reference ranges (2.5th\u0026ndash;97.5th percentiles) for morphological MRI parameters of the right and left fetal kidneys separately.\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" align=\"\" width=\"124%\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\"\u003e\n \u003cp\u003e\u003cstrong\u003eGestational week\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\"\u003e\n \u003cp\u003e\u003cstrong\u003enumber\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"4\"\u003e\n \u003cp\u003e\u003cstrong\u003eRight \u0026nbsp;renal\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"4\"\u003e\n \u003cp\u003e\u003cstrong\u003eLeft \u0026nbsp;renal\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e\u003cstrong\u003eLD\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e(cm)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u003cstrong\u003eTD (cm)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u003cstrong\u003eAD (cm)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u003cstrong\u003eMRPT (cm)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u003cstrong\u003eLD (cm)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u003cstrong\u003eTD (cm)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u003cstrong\u003eAD (cm)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u003cstrong\u003eMRPT (cm)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.01-2.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.33-1.44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.34-1.39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.53-0.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.00-2.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.26-1.31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.27-1.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.53-0.58\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.16-2.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.34-1.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.35-1.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.57-0.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.12-2.28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.35-1.47\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.38-1.48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.55-0.58\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.42-2.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.422-1.53\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.44-1.53\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.62-0.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.31-2.42\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.34-1.39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.35-1.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.56-0.62\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.69-2.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.63-1.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.66-1.73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.62-0.67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.57-2.74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.59-1.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.59-1.71\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.59-0.62\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.72-2.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.64-1.85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.58-1.80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.61-0.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.67-2.87\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.68-1.83\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.62-1.81\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.61-0.66\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.81-3.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.73-1.92\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.81-2.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.68-0.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.77-3.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.67-1.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.77-2.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.61-0.67\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.70-3.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.74-1.89\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.80-1.99\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.69-0.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.79-3.14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.73-1.88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.85-1.99\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.64-0.77\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3.30-3.39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.79-1.91\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.76-1.97\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.71-0.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3.24-3.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.85-1.94\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.83-2.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.67-0.75\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3.12-3.31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.81-1.96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.86-1.99\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.73-0.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3.08-3.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.80-1.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.74-1.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.75-0.81\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3.29-3.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.80-1.94\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.97-2.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.71-0.77\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3.20-3.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.85-1.97\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.93-2.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.73-0.78\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3.32-3.52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.97-2.14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.02-2.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.75-0.81\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3.43-3.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.91-2.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.95-2.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.74-0.81\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3.50-3.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.11-2.30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.08-2.24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.76-0.82\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3.45-3.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.11-2.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.10-2.26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.78-0.82\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3.44-3.77\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.10-2.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.05-2.31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.78-0.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3.68-3.98\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.01-2.22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.07-2.24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.82-0.97\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3.73-3.88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.28-2.51\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.19-2.47\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.79-0.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3.74-3.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.16-2.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.14-2.44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.80-0.91\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3.79-4.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.14-2.54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.33-2.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.78-0.85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3.82-4.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.23-2.71\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.11-2.48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.74-0.87\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e4.04-4.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.24-2.66\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.17-2.57\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.82-0.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e4.00-4.26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.17-2.55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.19-2.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e0.82-0.95\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eLD:longitudinal diameter(cm),TD:Transverse Diameter(cm),AD:Anteroposterior Diameter(cm),MRPT:Mean renal parenchymal thickness(cm).MRPT = (upper polar renal parenchymal thickness + renal hilar renal thickness + lower polar renal parenchymal thickness) .\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCorrelation Between Renal Parameters and Gestational Age\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSpearman correlation analysis demonstrated a moderate negative correlation between ADC and gestational age for both kidneys (right: r = \u0026minus;0.46, P \u0026lt; 0.0001; left: r = \u0026minus;0.52, P \u0026lt; 0.0001). RSI-T2 values showed a very weak to weak positive correlation with gestational age (right: r = 0.148; left: r = 0.200; both P \u0026lt; 0.0001). In contrast, Pearson correlation analysis revealed strong positive correlations between all morphological indicators and gestational age (all P \u0026lt; 0.0001):LD: r = 0.88 (right), r = 0.89 (left);TD: r = 0.78 (right), r = 0.80 (left);AD: r = 0.81 (right), r = 0.78 (left);MRPT: r = 0.72 (right), r = 0.74 (left).Scatter plots illustrating these relationships are shown in Figure 3 and Figure 4.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRegression Analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eGiven the negative correlation between ADC and gestational age as well as the positive correlation between MRPT and gestational age, linear regression models were constructed to characterize ADC and MRPT developmental trajectories.\u003c/p\u003e\n\u003cp\u003eRight kidney:ADC (\u0026times;10⁻\u0026sup3; mm\u0026sup2;/s) = 3.23 \u0026minus; 0.049 \u0026times; GA (weeks)(R\u0026sup2; = 0.218, P \u0026lt; 0.0001)\u003c/p\u003e\n\u003cp\u003eRight kidney:MRPT(cm)=0.026\u0026times; GA (weeks)-0.037(R\u0026sup2; = 0.518, P \u0026lt; 0.0001)\u003c/p\u003e\n\u003cp\u003eLeft kidney:ADC (\u0026times;10⁻\u0026sup3; mm\u0026sup2;/s) = 3.46 \u0026minus; 0.058 \u0026times; GA (weeks)(R\u0026sup2; = 0.273, P \u0026lt; 0.0001)\u003c/p\u003e\n\u003cp\u003eLeft kidney:MRPT(cm)=0.025\u0026times; GA (weeks)-0.027(R\u0026sup2; = 0.548, P \u0026lt; 0.0001)\u003c/p\u003e\n\u003cp\u003eThese models quantify the progressive decreases in ADC values and thickening of MRPT with advancing gestational age, establish predictive equations for clinical use.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this study, we established comprehensive multiparametric MRI reference ranges for normal fetal kidneys during the second and third trimesters, integrating both morphological and functional indicators. Our findings demonstrate that renal morphological parameters\u0026mdash;including LD, TD, AD, and MRPT\u0026mdash;show strong positive correlations with gestational age, whereas ADC values exhibit a moderate but significant decline with advancing gestation. Together, these results not only reflect the coordinated growth and maturation of fetal renal structures but also highlight the complementary value of combining morphologic and diffusion-based functional markers in evaluating fetal renal development.\u003c/p\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003ePhysiological Interpretation of Increasing Renal Parenchymal Thickness with Gestation\u003c/h2\u003e \u003cp\u003eOur results show a steady increase in MRPT from 23 to 38 weeks of gestation, with a strong correlation with GA (r\u0026thinsp;\u0026gt;\u0026thinsp;0.72). This pattern is in line with the established trajectory of renal development. After approximately 20 weeks, nephrogenesis gradually transitions from formation of new nephrons to hypertrophic growth of existing glomeruli and tubules \u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e. Although nephron number becomes largely fixed by 34\u0026ndash;36 weeks, tubular length, branching complexity, interstitial tissue volume, and vascular development continue to increase \u003csup\u003e[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e. These microstructural processes manifest as macroscopic thickening of the renal parenchyma, supporting MRPT as a reliable morphological indicator of renal maturation.\u003c/p\u003e \u003cp\u003eClinically, deviations from the gestational-age-specific MRPT reference range may serve as early warning signs of renal pathology. Reduced parenchymal thickness may indicate renal hypoplasia or congenital parenchymal disease, whereas compensatory hypertrophy secondary to obstructive uropathy or hereditary nephropathies may present as increased MRPT\u003csup\u003e[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e. Thus, MRPT provides a readily interpretable morphological marker with high clinical relevance in prenatal diagnostics .\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003eMechanisms Underlying the Decline in ADC Values With Advancing Gestation\u003c/h2\u003e \u003cp\u003eA notable finding of this study is the progressive decrease in renal ADC values with increasing gestational age, consistent with previous observations\u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e. This trend can be attributed to several physiological mechanisms:①Increasing cellular density and structural complexity:As nephrons proliferate and tubular structures elongate and thicken, the extracellular diffusion space becomes progressively restricted. This microstructural \u0026ldquo;densification\u0026rdquo; reduces the free movement of water molecules, directly contributing to lower ADC values\u003csup\u003e[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e.②Maturation of tubular transport function:During late gestation, the renal tubular epithelium undergoes functional maturation, leading to increasing reabsorption of water and solutes and the establishment of the corticomedullary osmotic gradient. Consequently, water molecules are increasingly compartmentalized within tubular and interstitial spaces, further restricting diffusivity\u003csup\u003e[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e.③Changes in renal perfusion contribution:Although absolute renal blood flow increases with gestation, its proportion of fetal cardiac output remains comparatively low (2%\u0026ndash;4%), substantially less than in neonates and adults. Thus, perfusion-related pseudodiffusion contributes minimally to the overall ADC signal during fetal life, reinforcing the dominant effect of structural restriction\u003csup\u003e[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe stronger negative correlation observed in the left kidney compared with the right may reflect subtle anatomical or physiological differences, though further investigation is warranted to clarify this asymmetry.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003eIntegrated Diagnostic Value of Morphological and Functional MRI Parameters\u003c/h2\u003e \u003cp\u003eThe combined analysis of structural and functional MRI parameters provides a more comprehensive assessment of fetal renal development. Morphological parameters, which increase linearly with gestational age, reflect macroscopic organ growth. In contrast, the decrease in ADC values captures microstructural maturation and functional development. The distinct but complementary patterns of change in these parameters underscore a morphology\u0026ndash;function dissociation that may enhance diagnostic precision.For example:Early renal hypoplasia may present as reduced MRPT with abnormally elevated ADC, indicating impaired parenchymal development and increased diffusivity.Early obstructive nephropathy may initially exhibit decreased ADC values, reflecting cytotoxic edema or early microstructural alterations, before morphological enlargement becomes apparent.Thus, integrating MRPT and ADC values may enable earlier and more accurate identification of subtle renal abnormalities compared with using either metric alone.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003eStudy Limitations\u003c/h2\u003e \u003cp\u003eSeveral limitations should be acknowledged. First, although the total cohort size was relatively large, certain late-gestation strata (\u0026ge;\u0026thinsp;37 weeks) contained fewer cases, which may slightly limit the robustness of reference ranges for these gestational ages. Second, the study was conducted at a single tertiary center, introducing potential selection bias and limiting generalizability to broader populations. Third, although measurement reproducibility was high, ADC values remain inherently sensitive to factors such as ROI placement, fetal motion, and sequence-specific technical parameters. Despite standardized protocols and repeatability assessments, residual variability is unavoidable. Future multicenter and prospective studies are needed to validate these findings across different MRI platforms and populations.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThis study established exploratory gestational age\u0026ndash;specific reference ranges for key morphological and functional MRI parameters of normal fetal kidneys. Renal size and parenchymal thickness increase steadily with gestation, reflecting macroscopic organ growth and providing robust quantitative markers for assessing structural development, whereas ADC values decline as a result of microstructural and functional maturation. Together, these markers offer a robust quantitative framework for evaluating fetal renal development. Their combined application may substantially enhance the prenatal detection, characterization, and prognostic assessment of fetal renal anomalies. Future multicenter studies are required to further validate these reference intervals and further explore their diagnostic utility in fetal renal disorders.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eADC\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eapparent diffusion coefficient\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eDWI\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003ediffusion-weighted imaging\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eGA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003egestational age\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eICC\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eintraclass correlation coefficient\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eMRI\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003emagnetic resonance imaging\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eMRPT\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003emean renal parenchymal thickness\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eROI\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eregion of interest\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eRSI-T2\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eT2 relative signal intensity\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eT2WI\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eT2-weighted imaging\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e \u003cp\u003eThis retrospective observational study was conducted at Sichuan Provincial Maternity and Child Health Care Hospital and was approved by the Medical Ethics Review Committee of Sichuan Provincial Maternity and Child Health Care Hospital (Approval No. 20240419-076).All procedures involving human participants were performed in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Declaration of Helsinki and its later amendments. Written informed consent to participate was obtained from all pregnant women prior to fetal MRI examination.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent for publication\u003c/strong\u003e \u003cp\u003eWritten informed consent for publication of anonymized clinical data and imaging was obtained from all participants and/or their legal guardians. The publication of anonymized data derived from this study was approved by the Medical Ethics Review Committee of Sichuan Provincial Maternity and Child Health Care Hospital (Approval No. 20240419-076).\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eCompeting interests\u003c/h2\u003e \u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eAuthors\u0026rsquo;information\u003c/h2\u003e \u003cp\u003eNot applicable.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThe authors received no specific funding for this work.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eYMP and MK conceived and designed the study and supervised the overall project. YMP, QYW, RL, and XJZ performed case selection, image review, data collection, and image and statistical analysis. SZM, as the radiologic technologist, conducted and coordinated the fetal MRI examinations and ensured image quality. YCL, as a research scientist from GE Healthcare, provided technical support for MRI sequence optimization and quantitative parameter implementation. YMP drafted the manuscript. All authors critically revised the manuscript for important intellectual content, approved the final version, and agreed to be accountable for all aspects of the work.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe authors would like to express their sincere gratitude to all patients and their families for their willingness to participate in this study and for their cooperation throughout the research period. The authors also thank the leadership and colleagues of the Department of Radiology, Sichuan Provincial Maternity and Child Health Care Hospital, for their continuous support. The approval and oversight provided by the Medical Ethics Committee of Sichuan Provincial Maternity and Child Health Care Hospital are gratefully acknowledged.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets that support the findings of this study are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eHill BJ, Joe BN, Qayyum A, et al. Supplemental value of MRI in fetal abdominal disease detected on prenatal sonography: preliminary experience.AJR. Am J Roentgenol. 2005;184(3):993\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCassart M, Massez A, Metens T, et al. Complementary role of MRI after sonography in assessing bilateral urinary tract anomalies in the fetus.AJR Am. J Roentgenol. 2004;182(3):689\u0026ndash;95.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVermoolen MA, Kwee TC, Nievelstein RA. Apparent diffusion coefficient measurements in the differentiation between benign and malignant lesions: a systematic review. Insights Imaging. 2012;3(4):395\u0026ndash;409.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eColagrande S, Carbone SF, Carusi LM, Cova M, Villari N. Magnetic resonance diffusion-weighted imaging: extraneurological applications. Radiol Med. 2006;111(3):392\u0026ndash;419. English, Italian.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePrasad PV, Priatna A. Functional imaging of the kidneys with fast MRI techniques. Eur J Radiol. 1999;29(2):133\u0026ndash;48.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eThoeny HC, De Keyzer F. Extracranial applications of diffusion-weighted magnetic resonance imaging. Eur Radiol. 2007;17(6):1385\u0026ndash;93.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAl Salmi I, Al Hajriy M, Hannawi SU. Measurement and Kidney Development: a Mini-Review for Nephrologists.Saudi. J Kidney Dis Transpl 2021 Jan-Feb;32(1):174\u0026ndash;82.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eManganaro L, Francioso A, Savelli S, Tomei A, Fierro F, Di Maurizio M, Coratella F, Perrone A, Ballesio L, Giancotti A, Porfiri L, Marini M. Fetal MRI with diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) assessment in the evaluation of renal development: preliminary experience in normal kidneys. Radiol Med. 2009;114(3):403\u0026ndash;13.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDos Santos Junior AC, de Miranda DM, Sim\u0026otilde;es e Silva AC. Congenital anomalies of the kidney and urinary tract: an embryogenetic review. Birth Defects Res C Embryo Today. 2014;102(4):374\u0026ndash;81. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1002/bdrc.21084\u003c/span\u003e\u003cspan address=\"10.1002/bdrc.21084\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWynyard P, Chitty LS. Dysplastic kidneys. Semin Fetal Neonat al Med. 2008;13:142\u0026ndash;51.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWoolf AS. A molecular and genetic view of human renal and urinary tract malformations. Kidney Int. 2000;58:500\u0026ndash;12.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSadler TW. The urogenital system. In: Sadler TW, editor. Langman\u0026rsquo;s Medical Embry ology. 9th ed. Baltimore, MD: Lippincott Williams \u0026amp; Wilkins; 2004. pp. 321\u0026ndash;62.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCuckow PM, Nyirady P, Winyard PJD. Normal and abnormal development of the urogenital tract. Prenat Diagn. 2001;21:908\u0026ndash;16.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFaghihimehr A, Gharavi M, Mancuso M, Sreedher G. Fetal MR imaging in urogenital system anomalies. J Matern Fetal Neonatal Med. 2019;32(20):3487\u0026ndash;94.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGubhaju L, Black MJ. The baboon as a good model for studies of human kidney development. Pediatr Res. 2005;58(3):505\u0026ndash;9. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1203/01.PDR.0000179397.20862.73\u003c/span\u003e\u003cspan address=\"10.1203/01.PDR.0000179397.20862.73\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAlmeida JR, Mandarim-de-Lacerda CA. Quantitative study of the comma-shaped body, S-shaped body and vascularized glomerulus in the second and third human gestational trimesters. Early Hum Dev. 2002;69(1\u0026ndash;2):1\u0026ndash;13.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLaissy JP, Id\u0026eacute;e JM, Fernandez P, Floquet M, Vrtovsnik F, Schouman-Claeys E. Magnetic resonance imaging in acute and chronic kidney diseases: present status. Nephron Clin Pract. 2006;103(2):c50\u0026ndash;7. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1159/000090609\u003c/span\u003e\u003cspan address=\"10.1159/000090609\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eObara M, Kwon J, Yoneyama M, Ueda Y, Cauteren MV. Technical Advancements in Abdominal Diffusion-weighted Imaging. Magn Reson Med Sci. 2023;22(2):191\u0026ndash;208. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.2463/mrms.rev.2022-0107\u003c/span\u003e\u003cspan address=\"10.2463/mrms.rev.2022-0107\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSavelli S, Di Maurizio M, Perrone A et al. MRI with diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) assessment in the evaluation of normal and abnormal fetal kidneys: Preliminary experience. Prenat Diagn, 27(12), 1104\u0026ndash;11.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-medical-imaging","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmim","sideBox":"Learn more about [BMC Medical Imaging](http://bmcmedimaging.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bmim/default.aspx","title":"BMC Medical Imaging","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"fetal kidney, magnetic resonance imaging, diffusion-weighted imaging, apparent diffusion coefficient, gestational age, renal development, reference values, prenatal diagnosis","lastPublishedDoi":"10.21203/rs.3.rs-8288896/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8288896/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eFetal renal developmental abnormalities are among the most common congenital malformations and are associated with adverse perinatal outcomes. However, existing fetal magnetic resonance imaging (MRI) studies are limited by small sample sizes and the lack of comprehensive gestational age (GA)\u0026ndash;specific reference ranges that integrate both morphological and functional parameters. This study aimed to establish multiparametric MRI reference ranges for normal fetal kidneys and to characterize their relationships with GA.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eIn this retrospective single-center observational study, 313 singleton pregnancies (GA 23\u0026ndash;39 weeks) with normal postnatal urinary outcomes underwent 1.5T fetal MRI, including T2-weighted and diffusion-weighted imaging sequences. Morphological parameters [anteroposterior, transverse and longitudinal diameters, and mean renal parenchymal thickness (MRPT)] and functional parameters [T2 relative signal intensity (RSI-T2) and apparent diffusion coefficient (ADC)] were measured for both kidneys. Reproducibility was assessed using intraclass correlation coefficients (ICC). Correlations between MRI parameters and GA were analyzed, and linear regression models were constructed for ADC.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eAll morphological and functional parameters demonstrated good to excellent intra- and inter-observer reproducibility (ICC\u0026thinsp;\u0026gt;\u0026thinsp;0.75). Renal diameters and MRPT increased significantly with GA (r\u0026thinsp;=\u0026thinsp;0.72\u0026ndash;0.89; all P\u0026thinsp;\u0026lt;\u0026thinsp;0.0001), reflecting progressive macroscopic growth. In contrast, ADC values decreased moderately with advancing GA (right kidney: r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.47; left kidney: r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.52; both P\u0026thinsp;\u0026lt;\u0026thinsp;0.0001), consistent with microstructural and functional maturation. The regression equations for ADC (\u0026times;10⁻\u0026sup3; mm\u0026sup2;/s) were: ADC_right\u0026thinsp;=\u0026thinsp;3.23\u0026thinsp;\u0026minus;\u0026thinsp;0.049 \u0026times; GA and ADC_left\u0026thinsp;=\u0026thinsp;3.46\u0026thinsp;\u0026minus;\u0026thinsp;0.058 \u0026times; GA.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eThis study provides GA-stratified reference ranges for key morphological and functional MRI parameters of normal fetal kidneys in the second and third trimesters. These quantitative benchmarks may improve prenatal assessment of fetal renal growth and maturation and support earlier detection and characterization of fetal renal developmental abnormalities.\u003c/p\u003e\u003ch2\u003eTrial registration\u003c/h2\u003e \u003cp\u003eNot applicable.\u003c/p\u003e","manuscriptTitle":"Establishment of Normal ADC Values and Morphological Parameters of the Fetal Kidney Using Magnetic Resonance Imaging and Analysis of their Correlation with Gestational Age","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-12 08:08:40","doi":"10.21203/rs.3.rs-8288896/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-03-02T09:47:15+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-02-20T10:50:02+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"303441438887869813263115658911671048968","date":"2026-01-19T22:31:37+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-13T12:59:51+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"186144465173886674309593113274352743312","date":"2026-01-07T17:56:16+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-07T17:45:42+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-01-05T09:39:45+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-12-17T10:08:05+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-12-17T06:54:27+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Medical Imaging","date":"2025-12-17T06:40:48+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-medical-imaging","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmim","sideBox":"Learn more about [BMC Medical Imaging](http://bmcmedimaging.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bmim/default.aspx","title":"BMC Medical Imaging","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"bc1f2935-08be-48f0-93b6-1866917b9148","owner":[],"postedDate":"January 12th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-03-06T14:38:21+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-12 08:08:40","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8288896","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8288896","identity":"rs-8288896","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}