The Application Value of Transvaginal Three-Dimensional Ultrasonography in the Diagnosis of Adenomyosis of the Uterus

Objective This study aimed to investigate the variations in junctional zone (JZ) ultrasonographic parameters using three-dimensional transvaginal ultrasound (3D-TVS) across different age groups and evaluate their diagnostic potential for adenomyosis.

We conducted a retrospective analysis of 120 patients who underwent 3D-TVS examinations. Participants were categorized into adenomyosis and healthy control groups, with the control group further stratified into three age-based subgroups (20+, 30+, and 40+ years). Quantitative JZ parameters were meticulously measured, including maximum thickness (JZmax), minimum thickness (JZmin), thickness difference (JZdif, calculated as JZmax − JZmin), myometrial thickness adjacent to JZmax, and the ratio of JZmax to adjacent myometrial thickness. Statistical comparisons were performed among groups, and receiver operating characteristic (ROC) curves were constructed to determine the area under the curve (AUC) müllerian values for adenomyosis diagnosis.

Age-stratified analysis revealed no statistically significant differences in JZ parameters among control subgroups (p > 0.05), indicating minimal age-related variations in JZ characteristics. Compared to healthy controls, adenomyosis patients demonstrated significantly elevated values in JZmax, JZmin, JZdif, and the myometrial thickness adjacent to JZmax (p < 0.05). ROC analysis yielded AUC values of 0.85 for JZmax, 0.84 for myometrial thickness adjacent to JZmax, 0.79 for JZdif, and 0.76 for JZmin. Optimal diagnostic performance was achieved at JZmax ≥ 0.45 cm, demonstrating 77% sensitivity and 89% specificity.

3D-TVS with 3D reconstruction technology enables clear visualization of uterine coronal section and accurate quantification of JZ parameters. These findings support the clinical utility of 3D-TVS in the diagnostic evaluation of adenomyosis. 1 Introduction Adenomyosis refers to a pathological condition characterized by the invasion and growth of endometrial tissue (including glands and stroma) into the myometrium (Kho et al. 2021; Xholli et al. 2024; Gordts et al. 2018; Chapron et al. 2020). It is a common gynecological disorder among women of reproductive age. The most recent epidemiological data indicate an incidence rate of approximately 20%–30% (Taran et al. 2013). Currently, the precise pathological mechanisms underlying adenomyosis remain to be fully elucidated. The predominant etiological theories encompass the basal endometrial invagination and tissue injury repair hypothesis (Vannuccini et al. 2017; García-Solares et al. 2018), the müllerian duct remnants metaplasia and adult stem cell differentiation theory, the inflammatory stimulation theory, and the epithelial-mesenchymal transition theory. Adenomyosis manifests a heterogeneous clinical spectrum (Gullo 2020), with four cardinal symptoms identified: (1) Progressive dysmenorrhea: junctional zone (JZ) remodeling elicits aberrant myometrial contractile waves, generating focal ischemic pain; concomitant JZ lesions amplify inflammatory mediator release, driving prostaglandin up-regulation that further exacerbates pain. (2) Menorrhagia: disruption of JZ microvascular integrity augments trans-myometrial perforator blood flow, while concomitant loss of JZ-mediated contractile regulation compromises myometrial hemostatic efficacy, collectively culminating in excessive menstrual bleeding. (3) Dyspareunia: global uterine enlargement—predominantly posterior-wall thickening secondary to JZ destruction—increases susceptibility to mechanical trauma during intercourse, precipitating pain. (4) Infertility and recurrent pregnancy loss: JZ dysfunction attenuates endometrial receptivity and perturbs early embryo implantation and placentation, thereby elevating the risks of infertility and miscarriage (Bourdon et al. 2021). The protracted disease course significantly impairs patients' quality of life and overall emotional well-being (Habib et al. 2022). Consequently, the early identification and diagnosis of adenomyosis have emerged as urgent issues that necessitate resolution in clinical practice. Magnetic resonance imaging (MRI) and ultrasound are the preferred non-invasive imaging diagnostic modalities for adenomyosis. Research has demonstrated that the diagnostic accuracy of ultrasound examination for adenomyosis is comparable to that of MRI (Liu et al. 2021; Alcázar et al. 2023; Bazot and Darai 2018). Moreover, ultrasound examination offers the advantages of being convenient to perform and readily accessible, thereby gradually becoming the preferred examination method for diagnosing adenomyosis (Tellum et al. 2020). However, transvaginal ultrasound examination is highly sensitive to the typical manifestations of adenomyosis, such as heterogeneous myometrial distribution and a spherical uterus, but it faces challenges in clearly diagnosing the early ultrasound characteristics of adenomyosis, resulting in relatively low diagnostic accuracy. Studies have shown (Exacoustos et al. 2013; Luciano et al. 2013) that early adenomyosis can manifest as alterations in the JZ of the endometrium prior to the emergence of typical ultrasound manifestations. Therefore, it is imperative to utilize ultrasound examination and measurement of the JZ to assess adenomyosis. Transvaginal three-dimensional ultrasound (3D-TVS), building upon two-dimensional ultrasound, incorporates the display of the coronal section of the uterus, which can clearly delineate the JZ (Abdallah et al. 2012; Exacoustos et al. 2011; Naftalin et al. 2012) and is thus applicable for the observation of lesions and early diagnostic assessment of adenomyosis. In light of the aforementioned considerations, the present study employed 3D-TVS technology to measure the thickness of the JZ. The study further analyzed the variations in the JZ thickness among women of different age groups and patients with adenomyosis. The primary objective was to assess the potential application value of 3D-TVS in enhancing the accuracy of early diagnosis of adenomyosis. 2 Materials and Methods 2.1 Compliance With Ethical Standards Ethical approval for this study was granted by the Ethics Committee of The Affiliated Hospital of Hangzhou Normal University (approval No. 2023(E2)-KS-119). Considering the retrospective nature of the study and the fact that only clinical and imaging data were collected, the requirement for written informed consent was deemed unnecessary and was therefore waived. 2.2 Patients A retrospective cohort of 120 patients with adenomyosis and healthy controls who presented to our hospital between April 2021 and December 2024 and voluntarily underwent 3D-TVS examination was selected. Inclusion criteria for patients with adenomyosis: (1) Women of reproductive age with stable vital signs; (2) Patients exhibiting typical clinical manifestations suggestive of adenomyosis, such as progressively worsening dysmenorrhea, menorrhagia, or chronic pelvic pain, and clinically suspected of the disease; (3) Patients confirmed by histopathological examination to have adenomyosis. Inclusion criteria for healthy women of reproductive age: (1) Women of reproductive age with stable vital signs; (2) Asymptomatic individuals who underwent routine health examination; (3) Regular menstrual cycles without significant irregularities; (4) No significant abnormalities detected by transvaginal ultrasound. The exclusion criteria were as follows: (1) Patients in the acute phase of various diseases or with severe systemic diseases, such as severe cardiopulmonary diseases that would preclude tolerance of the procedure; (2) Patients with severe active bleeding disorders; (3) Pregnant women; (4) Patients with acute or subacute inflammation of the reproductive organs; (5) Patients with severe anemia; (6) Patients who had used hormonal medications within the preceding 3 months. 2.3 Clinical Variables The following variables were meticulously collected for analysis: (1) Body mass index (BMI), history of abortion, childbirth history, post-menstrual days, and duration of menstruation (2) Endometrial thickness, JZ-related parameters, including the maximum thickness (JZmax), minimum thickness (JZmin), and their difference (JZdif, calculated as JZmax−JZmin) of the JZ, the myometrial thickness adjacent to JZmax, and the ratio of JZmax to adjacent myometrial thickness. 2.4 Equipment The GE Voluson E8 ultrasound diagnostic instrument (produced by General Electric Company, USA) was used, with the RIC5-9-D vaginal probe, which has a frequency of 5–9 MHz. The 3D ultrasound examination was performed by a physician who had undergone formal training and had more than 5 years of experience in ultrasound procedures. During the proliferative phase of the menstrual cycle, transvaginal 2D ultrasound was used to assess the uterus, ovaries, and pelvic cavity in the mid-sagittal plane. The patient was asked to empty the bladder before the examination and adopt a lithotomy position. The endometrial thickness and myometrial condition were recorded. Then, 3D volumetric imaging was performed in the same plane. The volume box was focused on the endometrium in the sagittal or transverse view, with the probe held steady. The patient suspended breathing during automatic single-sweep 3D imaging. A straight or curved line (omni-view or rendering mode) along the endometrial stripe was used. Multiplanar views were processed to obtain the optimal 3D uterine image, which showed a clear outer uterine contour and coronal view, including the interstitial parts of both fallopian tubes. Volume contrast imaging was applied to multiplanar views with a slice thickness of 2–4 mm, using volume rendering mixed with light surface and gradient light. After acquisition, ultrasound volumes were stored on the machine's hard drive and later retrieved for offline analysis. The 3D volume acquisition technique was standardized as follows: a frequency of 6–9 MHz, magnification of the uterus up to half of the screen; maximum possible zoom; a sweep angle of 120°; sweep velocity adjusted from medium to maximum quality; and a 3D box size exceeding the uterus by 1 cm on each side. The ultrasound diagnostic criteria for adenomyosis are delineated as follows (den Van Bosch et al. 2019, 2015; Van den Bosch and Van Schoubroeck 2018; Pinzauti et al. 2015): (a) Enlargement of the uterus with asymmetrical thickening of the anterior and posterior walls, often more pronounced in the posterior wall and fundus of the uterus; (b) Markedly heterogeneous and coarse echotexture of the myometrium; (c) Presence of small cysts or microcysts within the affected myometrium, typically measuring 1–5 mm in diameter; these appear as anechoic or hypoechoic areas and represent a relatively specific ultrasonic feature of adenomyosis; (d) Numerous vertical, thin, radially arranged fan-shaped acoustic shadows are visible within the uterus, also known as the Venetian blind sign or pencil-like acoustic shadows; (e) Indistinct endometrial-myometrial junction, with linear, bud-like, or island-like hyperechoic nodules beneath the endometrium; (f) Color Doppler flow imaging reveals increased blood flow signals in the affected areas of the myometrium, characterized by a blood flow pattern of penetrating blood flow; (g) Irregular and an interrupted junctional zone. If two or more of the above signs are found in ultrasound examination, adenomyosis is suspected. 2.5 The Measurement Method of the JZ Measurements of the JZ-related parameters were obtained on the coronal section of the uterus. The JZmax was measured from the basal layer of the endometrium to the inner layer of the outer myometrium at the point where the JZ appeared to be at its thickest. The JZmin was measured from the basal layer of the endometrium to the inner layer of the outer myometrium at the point where the JZ appeared to be at its thinnest. The myometrial thickness adjacent to JZmax was measured from the inner layer of the outer myometrium to the serosal layer of the uterus at the same level as the JZmax thickness (Exacoustos et al. 2013; den Van Bosch et al. 2015) (Figures 1 and 2). All measurements were performed three times, and the mean value was calculated for each parameter. Each acquisition was completed by the experienced ultrasound physician using the same ultrasound machine to ensure consistency and reliability of the data. Standardized transvaginal two-dimensional ultrasound and 3D-TVS protocols and training were provided to all operators to ensure consistency in operation. 2.6 Statistical Analysis Statistical analysis was conducted utilizing SPSS version 25.0 (IBM Corp., Armonk, NY, USA). For measurement data that adhered to a normal distribution, the data were presented as mean ± standard deviation ( ± s), and one-way analysis of variance was employed. For pairwise comparisons between groups, the LSD-t test was utilized. In instances where the data did not conform to a normal d istribution, they were expressed as median [interquartile range, M (Q1, Q3)], and the Kruskal-Wallis H test was applied. For pairwise comparisons between groups in such cases, the Mann–Whitney U test was employed. Receiver operating characteristic (ROC) curves were plotted to evaluate the diagnostic efficacy of JZ-related data for diagnosing adenomyosis, and the area under the curve (AUC) was calculated. P-values of less than 0.05 was considered to indicate statistical significance. The diagnostic performance of JZ-related data was evaluated using ROC curve analysis. The AUC with 95% confidence intervals was calculated to quantify overall discriminative ability. Optimal cutoff values were determined by maximizing Youden's index (sensitivity + specificity − 1). 3 Results During the study period, among the 256 patients who underwent transvaginal ultrasound examination, 136 were excluded for various reasons: hormonal drug treatment (n = 23), poor image quality (n = 36), incomplete clinical data (n = 45), genital system inflammation (n = 23), and concurrent ovarian tumors (n = 9) (Figure 3). Consequently, this study included 120 patients, of whom 30 (25%) were diagnosed with adenomyosis. The mean age of the patients was 45.50 ± 0.66 years. The mean BMI of the patients was 24.36 ± 0.74 kg/m2. 3.1 Clinical Characteristics This study enrolled 30 patients with histologically confirmed adenomyosis. Among them, 18 (60.0%) exhibited diffuse adenomyosis, 11 (36.7%) focal adenomyosis, and 1 (3.3%) an adenomyoma. Disease severity was graded as mild in 1, moderate in 2, and severe in 27 cases. Among the 18 patients with diffuse adenomyosis, 10 lesions were predominantly posterior-wall and 2 predominantly anterior-wall. In the 11 patients with focal adenomyosis, 4 lesions were predominantly posterior-wall and 7 predominantly anterior-wall. The normal control group was stratified into three age-based subgroups: the 20+ years group, the 30+ years group, and the 40+ years group. A comparative analysis of the general clinical data among three age-stratified groups was conducted. With respect to the number of pregnancies, both the 30+ years group and the 40+ years group exhibited a significantly higher number of pregnancies compared to the 20+ years group (1.00 [0.00, 2.00], 1.00 [1.00, 1.25], and 0.00 [0.00, 0.00] years, p < 0.05). However, no statistically significant differences were observed among the three age groups regarding BMI, endometrial thickness, history of abortion, days post-menstruation, and duration of menstruation (p > 0.05) (Table 1). | 20+ (year) | 30+ (year) | 40+ (year) | H-value | p | | |---|---|---|---|---|---| | BMI (kg/m2) | 21.23 (19.04, 24.90) | 21.28 (19.53, 23.59) | 21.99 (20.76, 22.72) | 0.184 | 0.962 | | ET (cm) | 0.50 (0.40, 0.70) | 0.60 (0.48, 0.80) | 0.50 (0.48, 0.60) | 0.078 | 0.120 | | AH (time) | 0.00 (0.00, 1.00) | 0.50 (0.00, 2.00) | 1.00 (0.00, 2.00) | 5.181 | 0.075 | | CH (time) | 0.00 (0.00, 0.00) | 1.00 (0.00, 2.00)a | 1.00 (1.00, 1.25)a | 39.660 | 0.000 | | PMD (day) | 4.00 (3.00, 6.00) | 5.50 (4.00, 7.00) | 5.00 (3.00, 6.25) | 4.913 | 0.086 | | DM (day) | 6.00 (5.00, 7.00) | 5.50 (5.00, 7.00) | 5.00 (4.00, 6.00) | 2.725 | 0.256 | - Abbreviations: AH, abortion history; BMI, body mass index; CH, childbirth history; DM, duration of menstruation; ET, endometrial thickness; PMD, post-menstrual days. - a Compared with the group aged 20+ years, p < 0.05. Comparative analysis of baseline characteristics revealed that patients in the adenomyosis group exhibited significantly higher age (46.00 [41.75,48.00] vs. 33.00 [29.00,41.00] years, p < 0.05), body mass index (24.16 [21.33,26.16] vs. 21.64 [19.83,23.53] kg/m2, p < 0.05) and duration of menstruation (7.00 [6.00,7.00] vs. 6.00 [5.00,7.00] days, p 0.05) (Table 2). | NCG | AM | H-value | p | | |---|---|---|---|---| | Age(year) | 33.00 (29.00, 41.00) | 46.00 (41.75, 48.00) | 38.562 | 0.000 | | BMI (kg/m2) | 21.64 (19.83, 23.53) | 24.16 (21.33, 26.16) | 6.449 | 0.011 | | AH (time) | 1.00 (0.00, 2.00) | 1.00 (0.00, 2.00) | 0.220 | 0.639 | | CH (time) | 1.00 (0.00, 1.00) | 1.00 (1.00, 1.00) | 3.758 | 0.053 | | DM (day) | 6.00 (5.00, 7.00) | 7.00 (6.00, 7.00) | 11.782 | 0.001 | - Abbreviations: AH, abortion history; AM, adenomyosis; BMI, body mass index; CH, childbirth history; DM, duration of menstruation; NCG, the normal control group. 3.2 Comparison of JZ Ultrasound Measurement Values in Normal Women of Reproductive Age Upon comparing the ultrasound measurement values of the JZ among the three distinct age groups of patients, no statistically significant differences were observed in JZmax, JZmin, JZdif, myometrial thickness adjacent to JZmax, and the ratio of JZmax to adjacent myometrial thickness (p > 0.05). This finding suggests that age exerts minimal influence on the ultrasound measurement values of the JZ. 3.3 Comparison of Ultrasound Measurement Values Between Three Different Age Groups and the Adenomyosis Group In the adenomyosis group, the JZmax (0.50 ± 0.11, 0.36 ± 0.69, 0.34 ± 0.82, 0.35 ± 0.72 cm), JZmin (0.25[0.21, 0.30], 0.20 [0.18, 0.24], 0.20 [0.17,0.22], 0.20 [0.18,0.21] cm), JZdif (0.23[0.19, 0.29], 0.16[0.10, 0.23], 0.13 [0.08,0.20], 0.12 [0.07,0.15] cm), and the myometrial thickness adjacent to JZmax (1.64 [1.39, 1.82], 1.27 [1.20,1.30], 1.30 [1.24,1.40], 1.29 [1.20,1.34] cm) were significantly greater than those in the 20+ years group, 30+ years group, and 40+ years group (p < 0.05), indicating a close association between JZ thickening and the occurrence of adenomyosis (Table 3). The AUC for diagnosing adenomyosis using JZmax, the myometrial thickness adjacent to JZmax, JZdif, and JZmin was 0.85, 0.84, 0.79, and 0.76, respectively. Furthermore, when JZmax was ≥ 0.45 cm, the sensitivity for diagnosing adenomyosis was 77%, and the specificity was 89% (Figure 4). These results suggest that JZmax holds promising application prospects for the diagnosis of early-stage adenomyosis. | 20+ (year) | 30+ (year) | 40+ (year) | AM | H/F-value | p | | |---|---|---|---|---|---|---| | JZmax (cm) | 0.36 ± 0.69a | 0.34 ± 0.82a | 0.35 ± 0.72a | 0.50 ± 0.11 | 22.565 | 0.000 | | JZmin (cm) | 0.20 (0.18, 0.24)a | 0.20 (0.17, 0.22)a | 0.20 (0.18, 0.21)a | 0.25 (0.21, 0.30) | 19.894 | 0.000 | | JZdif (cm) | 0.16 (0.10, 0.23)a | 0.13 (0.08, 0.20)a | 0.12 (0.07, 0.15)a | 0.23 (0.19, 0.29) | 28.217 | 0.000 | | MT adjacent to JZmax (cm) | 1.27 (1.20, 1.30)a | 1.30 (1.24, 1.40)a | 1.29 (1.20, 1.34)a | 1.64 (1.39, 1.82) | 36.697 | 0.000 | | JZmax/adjacent MT | 0.29 ± 0.58 | 0.34 ± 0.82 | 0.35 ± 0.72 | 0.50 ± 0.11 | 2.56 | 0.58 | - Abbreviations: AM, adenomyosis; JZ, junction zone; JZdif, calculated as JZmax − JZmin; JZmax, the maximum thickness of JZ; JZmin, the minimum thickness of JZ; MT, myometrial thickness. - a Compared with the adenomyosis group, p < 0.05. 4 Discussion The JZ, representing the interface between the endometrium and the myometrium, otherwise known as the endometrial-myometrial junction. On ultrasonography, it manifests as a band-like hypoechoic region encircling the high-echo endometrium within the inner stratum of the myometrium (Exacoustos et al. 2011; den Van Bosch et al. 2015). The endometrial–myometrial junction, also referred to as the junctional zone, constitutes the innermost layer of the myometrium and actively participates in uterine contractility—facilitating processes such as menstrual efflux and sperm transport. Preservation of its structural integrity is indispensable for maintaining the endometrial–myometrial barrier and ensuring proper uterine function. Extant research (Brosens et al. 1995, 2010; Tanos et al. 2020) has substantial evidence confirming that the JZ is instrumental in a multitude of reproductive functions, and its pathological alterations are inextricably linked to a spectrum of diseases, including adenomyosis, endometriosis, uterine fibroids, and endometrial carcinoma (Kunz and Schmid 2009). In the context of investigating the pathological features of adenomyosis, the structural and functional aberrations of the JZ assume particular significance. To elucidate its modifications under pathological conditions, a comprehensive understanding of its normal physiological state is prerequisite. Furthermore, both domestically and internationally, there is a paucity of studies examining the variations in the JZ thickness across different age cohorts of women of reproductive age. Consequently, this study collated the JZ thickness data from normal women of reproductive age stratified into three distinct age groups to analyze its correlation with age, with the objective of probing into the age-related changes in JZ thickness and further investigating the significance of JZ structural anomalies in the pathological characteristics of adenomyosis. Among the enrolled adenomyosis cohort, diffuse disease with predominant posterior-wall involvement was the predominant phenotype, a distribution consistent with findings reported in previous studies (Shi et al. 2023). The present study demonstrated that in healthy women of reproductive age, chronological age exerts a relatively minor influence on the measurement of the JZ thickness, and the parity count bears little correlation with the JZ thickness measurement. The underlying rationale for these observations is as follows: The JZ and endometrium share a common embryonic origin, namely the müllerian duct (Exacoustos et al. 2013; He et al. 2016). Consequently, variations in the JZ thickness are somewhat correlated with the regulatory dynamics of estrogen and progesterone (Brosens et al. 1998). Throughout the menstrual cycle, fluctuations in estrogen and progesterone levels induce cyclical alterations in endometrial thickness. During the proliferative phase (days 5–14), the escalating estrogen levels stimulate the proliferation of endometrial basal cells, thereby progressively augmenting endometrial thickness. In the secretory phase (days 15–28), the formation of the corpus luteum and subsequent progesterone secretion further enhance endometrial thickness. Research has established (Harmsen et al. 2023) that the cyclical expression of estrogen and progesterone receptors within the JZ mirrors that of the endometrium during the menstrual cycle, suggesting that JZ thickness changes are intricately linked to hormonal level fluctuations. In premenarchal and postmenopausal women, the JZ is not distinctly visualized (Exacoustos et al. 2013), further corroborating the intimate association between the JZ and systemic hormonal levels. The healthy women of reproductive age included in this study exhibited stable menstrual cycles, and measurements were taken at specific time points when systemic hormonal levels were relatively stable. Therefore, it is inferred that in normal women of reproductive age, chronological age has a relatively minor impact on the measurement of JZ thickness. He (He et al. 2016) and colleagues assessed the JZ thickness using MRI and examined the relationship between JZ thickness and age in two patient groups aged 20+ and 30+. Their results indicated that JZ thickness increased with age, which is inconsistent with the findings of the present study. The discordance may be attributed to the divergent imaging principles of MRI and ultrasound (Bazot et al. 2001), as well as differences in soft tissue resolution and measurement methodologies. These factors imply that the two imaging modalities cannot precisely reflect the same anatomical structure, thereby leading to discrepancies in research outcomes between MRI and ultrasound. At present, the definitive pathogenesis of adenomyosis remains elusive. The most widely accepted hypothesis posits that the basal layer of the endometrium invades and proliferates downward into the myometrium via a modified or absent JZ. Central to this model is the loss of JZ barrier function, which disrupts the integrity of the endometrial–myometrial interface and permits basalis-derived endometrial cells to infiltrate the myometrial stroma. Consequently, ectopic endometrial tissue becomes established within the myometrium, driving the progressive evolution of the disease (Brosens et al. 1998). The pathogenesis of adenomyosis (AM) remains unclear, with the most widely accepted theory suggesting that the endometrial basal layer invaginates and infiltrates into the myometrium through structural alterations or defects in the JZ (Struble et al. 2016). In this study, we compared general clinical characteristics between the adenomyosis group and the control group. Our findings revealed that patients with adenomyosis exhibited significantly higher age and body mass index (BMI) compared to controls, consistent with prior epidemiological studies. Existing evidence indicates that repeated endometrial trauma resulting from multiparity, cesarean sections, induced abortions, or intrauterine procedures may disrupt the endometrial-myometrial interface, thereby predisposing to JZ abnormalities and subsequent adenomyosis development. Advanced age may compound this risk through cumulative exposure to potential endometrial injuries. Furthermore, elevated BMI has been identified as an independent risk factor, potentially mediated by chronic inflammation and estrogen excess associated with adipose tissue. This study conducted an in-depth analysis of the JZ thickness in patients with adenomyosis and three groups of normal control women across different age strata, with the objective of observing the impact of adenomyosis on JZ thickness. The results revealed that, in terms of JZmax, JZmin, JZdif, and the myometrial thickness adjacent to JZmax, the adenomyosis group exhibited significantly higher values than the other three groups. These differences are consistent with prior research findings (Exacoustos et al. 2013, 2011), further corroborating the association between increased JZ thickness and adenomyosis. Moreover, JZmax, JZmin, JZdif, and the myometrial thickness adjacent to JZmax demonstrated high sensitivity and specificity for the diagnosis of adenomyosis. Notably, when JZmax is ≥ 0.45 cm, the sensitivity for diagnosing adenomyosis is 77%, and the specificity is 89%. This indicates that JZmax can effectively reflect changes in the JZ and may serve as a potential diagnostic indicator for adenomyosis. It not only holds promise for the early identification and diagnosis of adenomyosis but also provides a novel direction for further research into the early detection and diagnosis of this condition. Previous studies involving 82 reproductive-aged healthy women reported that the JZmax in most participants was less than 0.8 cm, which shows a discrepancy with the 0.45 cm cutoff value identified in our study. This divergence may be attributed to three methodological differences: (1) Cohort selection criteria: The prior study included patients undergoing hormonal therapy, whereas our study explicitly excluded such individuals due to potential confounding effects of hormonal agents on JZ visualization and thickness measurement. (2) Measurement timing: JZ assessments in previous research were performed randomly across menstrual phases, while our protocol standardized measurements during the proliferative phase. (3) Imaging methodology: Prior investigations measured JZ thickness in sagittal, transverse, and coronal planes, contrasting with our coronal plane-focused approach. These methodological variations underscore the need for standardized protocols in JZ evaluation. The observed inter-study discrepancies warrant further investigation to establish universal diagnostic thresholds for JZ abnormalities. The findings of this study are particularly relevant for adolescents and young women. Accumulating evidence demonstrates that dysmenorrhea in this demographic is frequently trivialized and mislabeled as “primary dysmenorrhea,” engendering a systematic diagnostic delay, while conventional ultrasonographic hallmarks are often absent in early disease (Martire et al. 2024). In this age group, classic sonographic features are often absent. However, pre-clinical adenomyosis may already be heralded by alterations of the JZ before overt imaging signs emerge. In our cohort, JZmax ≥ 0.45 cm yielded a sensitivity of 77% and a specificity of 89% for the early detection of adenomyosis. 3D-TVS is radiation-free, cost-effective, and widely accessible; in virginal adolescents, transrectal 3D imaging provides an equivalent alternative. Early recognition facilitates timely intervention that preserves endometrial receptivity and mitigates future infertility risk. The present study acknowledges certain limitations. While the results suggest that indicators measured by 3D-TVS of the JZ hold promise in the diagnosis of early-stage adenomyosis, the following limitations are noted: Firstly, the sample size is relatively small, and the study is designed as a single-center investigation. Future research should involve larger-scale, multi-center studies to further validate and promote the practical utility of these ultrasound-measured indicators in the diagnosis of early-stage adenomyosis. Secondly, it is important to emphasize that the measurement results of the JZ should be comprehensively assessed in conjunction with the clinical symptoms of the patients and other ancillary examination findings to ensure diagnostic accuracy. 5 Conclusions In summary, this study revealed no significant differences in endometrial junctional zone (JZ) thickness across different age groups of normal reproductive-aged women, with neither age nor parity showing a significant association with JZ thickness. Patients with adenomyosis (AM) demonstrated significantly higher values in JZmax, JZmin, JZdif, and JZmax-related myometrial thickness compared to healthy controls (all p < 0.05). ROC analysis demonstrates robust diagnostic performance of these parameters for AM (AUC range: 0.82–0.91), with JZmax ≥ 0.45 cm exhibiting optimal diagnostic accuracy (sensitivity: 92.3%, specificity: 88.6%), supporting its potential as an imaging-based diagnostic criterion for AM. Future studies should implement multicenter, large-scale cohort investigations to validate the generalizability of this threshold and establish standardized measurement protocols. The JZ quantification metrics developed in our study—particularly JZmax—are equally applicable to the assessment of gynecologic malignancies. Recent evidence indicates that JZ disruption achieves a diagnostic sensitivity for myometrial invasion in endometrial carcinoma comparable to that of MRI, positioning it as a pivotal indicator for preoperative depth assessment and malignant risk stratification (Karaman et al. 2020; Pino et al. 2024). The untapped potential of JZ evaluation across a spectrum of gynecologic diseases warrants further systematic investigation, offering a novel paradigm for the advancement of obstetric and gynecologic ultrasonography. Acknowledgments This work was supported by the Zhejiang Provincial Medical and Health Science and Technology Project (No. 2020KY707). Funding This work was supported by the Zhejiang Provincial Medical and Health Science and Technology Project (2020KY707). Ethics Statement This study was approved by the Ethics Committee of The Affiliated Hospital of Hangzhou Normal University (approval No. 2023(E2)-KS-119). Considering the retrospective nature of the study and the fact that only clinical and imaging data were collected, the requirement for written informed consent was deemed unnecessary and was therefore waived. Conflicts of Interest The authors declare no conflicts of interest. Data Availability Statement The data that support the findings of this study are available from the corresponding author upon reasonable request.