Pediatric Renal Abscess: A 12-year Single-Center Retrospective Analysis

Pediatric Renal Abscess: A 12-year Single-Center Retrospective Analysis | 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 Pediatric Renal Abscess: A 12-year Single-Center Retrospective Analysis Jian-Qun Guo, Mei-Hao Gao, Yi-Jiao Ma, Shi-Lei Jia, Xiao-Jie Gao, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7531142/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 27 Mar, 2026 Read the published version in Pediatric Nephrology → Version 1 posted 5 You are reading this latest preprint version Abstract Background Renal abscesses are infrequent but serious consequences of urinary tract infections in children, frequently manifesting with nonspecific symptoms that might postpone diagnosis. Research on pediatric renal abscesses is limited. Methods This retrospective study investigated 69 children with radiologically verified renal abscesses from November 2012 to February 2024. Patients were categorized into three age groups: 1–24 months, 25–60 months, and over 60 months. Clinical features, laboratory and imaging results, and therapy outcomes were assessed. Results The median age was 24.0 months (IQR: 7.3, 66.8) and the male-to-female ratio of 35:34. Age-stratified analysis revealed a male predominance in the 1–24-month group (26 males vs. 9 females) and a female predominance in the > 60-month group (17 females vs. 2 males). Fever was noted in 98.6% (68/69), abdominal pain in 29.0% (20/69) and gastrointestinal symptoms in 26.1% (18/69). Ultrasound identified enlarged kidneys in 52.2% (36/69) of cases. The sensitivity of renal ultrasound was 40.4% (61/151). Vesicoureteral reflux was observed in 52.6% (20/38) of cases. Urine cultures demonstrated positive results in 34.8% (24/69) of cases, with Escherichia coli (37.5%, 9/24) and Enterococcus species (25.0%, 6/24) identified as the predominant pathogens. Surgical intervention was required in 7.2% (5/69) of cases, and 7.2% (5/69) developed acute kidney injury. The median duration of hospital stay was 12.0 days (IQR: 9.0, 15.0), with an extension observed in cases of left-sided or bilateral involvement (adjusted P = 0.0315, 0.0327). Conclusion This study highlights the diagnostic importance of enhanced CT/MRI and the significance role of vesicoureteral reflux in pediatric renal abscesses. renal abscess children enhanced CT/MRI vesicoureteral reflux Figures Figure 1 Introduction Renal abscesses are localized accumulations of purulent fluid within the kidneys, representing a rare but severe complication of urinary tract infections (UTIs) [ 1 ]. They generally emerge not as distinct entities but as a continuum from acute focal bacterial nephritis (AFBN) or persistent UTIs. The fundamental pathology includes significant vasospasm, inflammation, and liquefactive necrosis. The incidence of renal abscesses remains unclear. Improvements in imaging technologies, especially contrast-enhanced computed tomography (CT) or magnetic resonance imaging (MRI), have markedly enhanced detection rates[ 2 , 3 ]. Nevertheless, timely diagnosis remains challenging due to the nonspecific nature of symptoms, which often overlap with those of common UTIs. Early detection and intervention are critical to prevent severe consequences such as renal impairment or sepsis[ 4 , 5 ]. In pediatric patients, renal abscesses are frequently attributed to congenital abnormalities of the urinary tract, including vesicoureteral reflux (VUR), structural ureter and bladder anomalies, and duplicated renal systems[ 6 ]. These conditions predispose children to recurrent infections that may progress to abscess formation. Bacteremia can also contribute to abscess formation. The incidence of renal abscesses caused by Streptococcus has decreased due to advancements in vaccination and antibiotics. However, Escherichia coli and other gram-negative bacteria have emerged as the main pathogens[ 7 – 9 ]. Notably, the emerging role of Enterococcus species as a causative agent, particularly in regions with distinct resistance patterns, remains inadequately explored, highlighting a significant knowledge gap. The existing literature on renal abscesses exhibits several limitations. Studies often focus on general disease aspects, neglecting important factors such as age-specific traits and the comparative diagnostic effectiveness of imaging techniques. Additionally, limited sample sizes in numerous studies compromise the strength and applicability of results. Ultrasound, commonly employed for initial screening in diagnostics, exhibits limited accuracy, particularly for small or early-stage abscesses. While contrast-enhanced CT and MRI offer more reliable diagnostic tools, the establishment of standardized diagnostic threshold (e.g., specific CT value differences) for abscess identification remain undefined. One area of uncertainty pertains to the role of VUR. The prevalence of VUR in children with renal abscesses, despite being acknowledged as a risk factor, remains inadequately defined. Consequently, a consensus on the necessity of routine post-infection voiding cystourethrogram (VCUG) for evaluating VUR in this population remains absent. The existing knowledge gaps contribute to an inadequately defined clinical profile and diagnostic strategy for renal abscesses in pediatric patients. This study investigates the clinical and etiological characteristics of renal abscesses in children, focusing on age-specific characteristics, microbial pathogen distribution, and imaging and laboratory findings. This study aims to rectify existing deficiencies and enhance the understanding of pediatric renal abscesses within this particular population. Methods Study Design The research enrolled 69 patients diagnosed with renal abscesses at Shenzhen Children’s Hospital in Guangdong Province, China, from November 2012 to February 2024. Out of 151 cases initially screened for suspected renal abscesses, 69 were confirmed eligible after evaluation with contrast-enhanced CT or MRI. All patients received initial renal ultrasound screening to detect potential abnormalities. The inclusion criteria required a definitive diagnosis through contrast-enhanced CT or MRI. Renal abscesses were characterized as: (1) on contrast-enhanced CT, well-defined hypodense lesions (typically 0–20 Hounsfield Units) with rim enhancement and often accompanied by perinephric fat stranding or fluid collections[ 10 ]; or (2) on MRI, lesions exhibiting T2-hyperintensity, T1-hypointensity, rim enhancement on post-contrast T1-weighted imaging, and restricted diffusion on diffusion-weighted imaging (DWI) with low apparent diffusion coefficient (ADC) values[ 11 ]. Cases diagnosed exclusively through renal ultrasound were excluded because of its lower sensitivity and specificity in confirming renal abscesses. Data Collection Patients were categorized into three age groups according to developmental and clinical relevance: (1) infants and toddlers (1–24 months), (2) preschool children (25–60 months), and (3) school-age children (> 60 months). Demographic data, clinical symptoms, imaging findings, and laboratory results were obtained from electronic medical records. Structural urinary abnormalities were evaluated through renal ultrasound, contrast-enhanced CT/MRI, or VCUG. Statistical Analysis Continuous variables were summarized as mean ± standard deviation (SD) for normally distributed data and median with interquartile range (IQR) for non-normally distributed data, as assessed by the Shapiro-Wilk test. The Student’s t-test was utilized for pairwise comparisons of normally distributed data, whereas the Mann-Whitney U test was employed for non-normally distributed data. One-way analysis of variance (ANOVA) was utilized for normally distributed data in multiple group comparisons, while the Kruskal-Wallis test was applied for non-normally distributed data. Categorical variables were assessed through the Chi-square test or Fisher’s exact test when expected cell counts were less than 5. The Bonferroni correction was utilized to account for multiple comparisons. A two-tailed P-value of less than 0.05 was deemed statistically significant. Data analysis was conducted utilizing GraphPad Prism version 9.5.0. Results Clinical Characteristic The study comprised 69 patients diagnosed with renal abscesses, exhibiting a median age of 24 months (interquartile range [IQR]: 7.3, 66.8 months) and a male-to-female ratio of 35:34. Age-stratified analysis indicated a male predominance in the 1–24-month age group (26 males compared to 9 females), while females were predominated in the > 60-month age group (17 females compared to 2 males). In terms of abscess location, left-sided abscesses were identified in 32 patients (46.4%), right-sided abscesses in 30 patients (43.5%), and bilateral abscesses in 7 patients (10.1%). The most common clinical manifestations include fever, present in 98.6% of patients (68/69), followed by gastrointestinal symptoms (vomiting, diarrhea, and nausea) in 26.1% (18/69) and abdominal pain in 29.0% (20/69). Infrequent symptoms were reported, including loin pain in 5.8% (4/69), abdominal distension in 1.4% (1/69), and respiratory symptoms in 14.5% (10/69). Neurological manifestations occurred in 5.8% of cases (4/69), whereas urinary smell and oliguria were each observed in 1.4% (1/69). Furthermore, 20.3% of patients (14/69) experienced recurrent urinary tract infections (UTIs), whereas 5.8% (4/69) had a documented history of fever of unknown origin, as presented in Table 1 . Table 1 Demographic and clinical characteristics of pediatric patients with renal abscesses, stratified by age group. Variables All patients (N = 69) 1–24 months (N = 35) 25–60 months (N = 15) > 60 months (N = 19) P value Gender < 0.0001 Male 50.7% (35/69) 74.3% (26/35) 46.7% (7/15) 10.5% (2/19) Female 49.3% (34/69) 25.7% (9/35) 53.3% (8/15) 89.5% (17/19) Age-Group distribution 100% (69/69) 50.7% (35/69) 21.7% (15/69) 27.6% (19/69) Median age (months) 24.0 (IQR: 7.3–66.8) 7.3 (IQR: 4.0–9.5) 43.4 (IQR: 36.0-53.8) 90.0 (IQR: 78.1–106.8) < 0.0001 Abscess location 0.942 Left kidney 46.4% (32/69) 45.7% (16/35) 46.7% (7/15) 47.4% (9/19) Right kidney 43.5% (30/69) 42.9% (15/35) 40.0% (6/15) 47.4% (9/19) Bilateral 10.1% (7/69) 11.4% (4/35) 13.3% (2/15) 5.2% (1/19) Recurrent infection * 26.1% (18/69) 37.1% (13/35) 6.7% (1/15) 21.5% (4/19) 0.045 Hospital stays (days) 12.0 (IQR: 9.0–15.0) 12.0 (IQR: 9.0-15.6) 14.0 (IQR: 10.5–15.5) 11.0 (IQR: 9.5–13.0) 0.3723 Symptoms Fever 98.6% (68/69) 97.1% (34/35) 100.0% (15/15) 100.0% (19/19) Abdominal pain 29.0% (20/69) - † 53.3% (8/15) 63.2% (12/19) Vomiting and diarrhea 26.1% (18/69) 11.4% (4/35) 53.3% (8/15) 31.6% (6/19) Cough and runny nose 14.5% (10/69) 20.0% (7/35) 6.7% (1/15) 10.5% (2/19) Loin pain 5.8% (4/69) - † 6.7% (1/15) 15.8% (3/19) Abdominal distension 1.4% (1/69) - † 0.0% (0/15) 5.3% (1/19) Dysuria 5.8% (4/69) 2.9% (1/35) 0.0% (0/15) 15.8% (3/19) Ultrasound abnormalities Enlarged kidney 52.2% (36/69) 48.6% (17/35) 60.0% (9/15) 52.6% (10/19) 0.75 Hydronephrosis 29.0% (20/69) 40.0% (14/35) 13.3% (2/15) 21.1% (4/19) 0.089 Ureteral dilation 13.0% (9/69) 22.9% (8/35) 0.0% (0/15) 5.3% (1/19) 0.023 Duplicated system 4.3% (3/69) 0.0% (0/35) 13.3% (2/15) 5.3% (1/19) 0.091 VUR Detection 52.6% (20/38) 62.5% (15/24) 16.7% (1/6) 50.0% (4/8) 0.042 Elevated markers Blood WBC ‡ 65.2% (45/69) 62.9% (22/35) 66.7% (10/15) 68.4% (13/19) 0.895 Blood CRP ‡ 85.5% (59/69) 82.9% (29/35) 93.3% (14/15) 84.2% (16/19) 0.674 Urine WBC 78.3% (54/69) 85.7% (30/35) 46.8% (7/15) 89.5% (17/19) 0.005 Urine RBC 39.1% (27/69) 31.4% (11/35) 46.8% (7/15) 47.4% (9/19) 0.379 Urine LE § 59.4% (41/69) 71.4% (25/35) 33.3% (5/15) 57.9% (11/19) 0.022 Treatment outcomes Surgical intervention ¶ 7.2% (5/69) 5.7% (2/35) 13.3% (2/15) 5.3% (1/19) 0.615 Acute kidney injury # 7.2% (5/69) 11.4% (4/35) 6.7% (1/15) 0.0% (0/19) 0.246 Notes: * represents cases with recurrent urinary tract infections and recurrent fever of unknown origin. † indicates that patients under 24 months of age are often unable to express feelings of abdominal pain or loin pain or abdominal distension. ‡ denotes elevated with white blood cell count (WBC > 15 × 10⁹/L) or C-reactive protein (CRP > 30 mg/L). § represents Leukocyte Esterase (LE), a urinary marker of infection. ¶ refers to surgical intervention, defined as drainage or surgical procedures for renal abscesses.# indicates acute kidney injury (AKI), classified according to the pRIFLE (Pediatric Risk, Injury, Failure, Loss, End Stage Renal Disease) criteria. Imaging Findings Ultrasound detected urinary tract abnormalities in approximately half of the cases, with enlarged kidneys in 52.2% (36/69), hydronephrosis in 29.0% (20/69), ureteral dilation in 13.0% (9/69), and duplicated collecting systems in 4.3% (3/69) (Table 1 ). Among these 69 patients, 8 exhibited normal renal ultrasound findings at presentation, subsequently confirmed as renal abscesses by enhanced CT or MRI, resulting in an ultrasound sensitivity of 40.4% (61/151). Imaging modalities included enhanced CT in 64 patients (92.8%, 64/69) and enhanced renal MRI in 8 patients (11.6%, 8/69), with 3 patients receiving both procedures simultaneously. The minimum CT value in the abscess area was 20.7 ± 7.6 Hounsfield Units (HU) in 35 of the 69 patients with documented CT values in radiology reports. The CT value difference between the abscess area and adjacent normal tissue was 28.8 ± 8.0 HU in 37 of the 69 patients with documented CT value differences in radiology reports. Analysis of abscess diameters in the left (n = 19) and right (n = 11) kidneys indicated significantly larger diameters in the left kidney for the craniocaudal (CC) dimension (23.93 ± 11.79 mm vs. 12.76 ± 5.58 mm; P = 0.0065) and anteroposterior (AP) dimension (21.16 ± 8.69 mm vs. 12.55 ± 4.65 mm; P = 0.0052). No significant difference was observed in the transverse (TR) dimension (19.65 ± 8.76 mm vs. 13.69 ± 5.91 mm; P = 0.0552) (Fig. 1 A and 1 C). Of the 69 patients, 44.9% (31/69) refused VCUG, which restricts the evaluation of VUR. Among the 38 patients who underwent VCUG, 52.6% (20/38) were diagnosed with VUR, of which 45.0% (9/20) exhibited bilateral involvement (Table 2 ). Age-stratified analysis of VCUG results indicated that VUR were present in 62.5% (15/24) of the 1–24-month group, 16.7% (1/6) of the 25–60-month group, and 50.0% (4/8) of the > 60-month group. Additionally, 11, 9, and 11 patients from each respective group did not undergo VCUG. Three patients present with distinct conditions: one exhibits bilateral vesicoureteral reflux (VUR), megaureter, and left ureteropelvic junction stenosis (UPJO); another has right-sided Grade III VUR, megaureter, ureteral diverticulum, and neurogenic bladder; and the third is diagnosed with left ureteral segmental stenosis via intravenous pyelogram (IVP). Table 2 Grading distribution of vesicoureteral reflux (VUR) detected by voiding cystourethrography (VCUG) in the evaluated pediatric renal abscess cohort. Category Frequency(n) Percentage (%) VCUG Assessment Status Unassessed 31 44.9% (31/69) Evaluated 38 55.1% (38/69) VUR Diagnosis (N = 38) No VUR detected 18 47.4% (18/38) VUR present 20 52.6% (20/38) Left VUR - Left Grade II 1 2.6% (1/38) - Left Grade III 5 13.2% (5/38) - Left Grade IV 1 2.6% (1/38) Right VUR - Right Grade III 3 7.9% (3/28) - Right Grade IV 1 2.6% (1/38) Bilateral VUR - Right Grade I, Left Grade V 1 2.6% (1/38) - Right Grade II, Left Grade II 1 2.6% (1/38) - Right Grade III, Left Grade I 2 5.3% (2/38) - Right Grade III, Left Grade II 2 5.3% (2/38) - Right Grade III, Left Grade III 2 5.3% (2/38) - Right Grade IV, Left Grade III 1 2.6% (1/38) Laboratory Findings: Most of the 69 patients exhibited elevated systemic inflammation markers. C-reactive protein was elevated in 85.5% (59/69) of cases, blood leukocytosis was observed in 65.2% (45/69), urine white blood cells were present in 78.3% (54/69), urine red blood cells were found in 39.1% (27/69), and leukocyte esterase was detected in 59.4% (41/69). Urine cultures revealed pathogens in 34.8% of cases (24/69). Escherichia coli was identified in 37.5% (9/24) of these instances, followed by Enterococcus species at 25.0% (6/24), Enterobacter cloacae at 8.3% (2/24), Klebsiella species at 4.2% (1/24), Candida glabrata at 4.2% (1/24), and Corynebacterium glucuronolyticum at 4.2% (1/24). One patient identified an unclassified Gram-negative bacterium with a low count attributed to prior antibiotic administration. Blood cultures were performed in 66 out of 69 patients. The results were positive in 3.0% (2/66), identifying Klebsiella pneumoniae and Streptococcus constellatus. Purulent fluid cultures from renal abscesses in two patients were positive for Klebsiella pneumoniae and Streptococcus constellatus. Treatment Outcomes All 69 patients were administered empirical antibiotic therapy. Surgical intervention, including drainage or nephrectomy, was required in 7.2% of cases (5/69) due to the progression of abscesses or perirenal extension. Acute kidney injury (AKI) was also observed in 7.2% of patients (5/69), with resolution achieved through conservative management within 4 weeks. The median duration of hospital stay was 12.0 days (interquartile range [IQR]: 9.0, 15.0 days), with no statistically significant difference observed among the three age groups (P = 0.3723) (Table 1 ). However, patients with left-sided or bilateral kidney involvement had a longer hospital stay than those with right-sided kidney involvement, with statistically significant differences (adjusted P = 0.0315 for left-sided, P = 0.0327 for bilateral). Discussion Renal abscess, a rare but serious inflammatory condition characterized by purulent collections within the renal parenchyma. Diagnosis has historically been difficult due to limited imaging techniques, often resulting in delayed recognition, extended hospitalization or the need for invasive procedures[ 12 ]. Recent advancements in antimicrobial therapy and imaging technologies, including contrast-enhanced CT and MRI, have improved detection rates. Nonetheless, renal abscesses continue to be underrecognized in clinical practice, especially in pediatric populations[ 13 ]. This retrospective study from a single center constitutes the largest cohort of pediatric renal abscess cases reported to date. The aim was to outline the clinical, diagnostic, and therapeutic characteristics of renal abscesses in pediatric patients. Fever was noted in almost all patients within our cohort. Furthermore, 20.3% (14/69) exhibited a history of recurrent urinary tract infections, while 5.8% (4/69) presented with recurrent fever of unknown origin. These findings are consistent with prior research[ 6 ] and indicate a more robust association between recurrent UTIs and the development of renal abscesses. Our cohort demonstrated no significant gender difference in pediatric renal abscesses, which contrasts with previous studies indicating a female predominance[ 6 , 14 ]. Age stratification revealed a male predominance in infants (26 vs. 9, 1–24 months) and a female predominance in older children (17 vs. 2, > 60 months). The findings correspond with gender-specific patterns of UTIs, indicating that renal abscesses are predominantly a result of ascending infections. Renal abscesses may develop on either side of the kidney; however, our study suggests a higher prevalence of unilateral involvement. Nonetheless, no significant difference was observed between left- and right-sided involvement, which contradicts earlier studies indicating a higher incidence of right-sided abscesses[ 14 – 16 ]. The finding that patients with left-sided or bilateral renal abscesses had longer hospital stays than those with right-sided involvement indicates possible variations in disease severity or management difficulties. This finding may indicate anatomical complexity or larger abscess volumes on the left side, as evidenced by significant diameter differences in the craniocaudal and anteroposterior dimensions, potentially requiring prolonged antibiotic therapy or increased monitoring for surgical intervention. This suggests a potential benefit in customizing treatment duration and monitoring intensity based on abscess location and size, an area warranting further investigation. The urine culture positivity rate of 34.8% is considerably lower than findings in earlier studies[ 6 , 15 , 17 , 18 ], probably attributable to prior antibiotic administration before admission. This also indirectly highlights the problem of inappropriate antibiotic use in Shenzhen, specifically the lack of culture specimen collection prior to antibiotic administration. The prevalence of gram-negative pathogens, notably Escherichia coli (37.5%), indicates that initial empirical antibiotic therapy should focus on this group, while also considering Enterococcus species (25.0%) in the context of local resistance patterns. The incidence of Enterococcus species notably surpasses findings from other pediatric cohorts[ 6 , 15 ], which may indicate regional variations in antibiotic usage, microbial resistance, or healthcare practices. Ultrasound serves as a basic screening method for renal abscesses, unaffected by impaired renal function or complications arising from contrast material allergies[ 19 ]. Renal enlargement identified via ultrasound was observed in 52.2% (36/69) of patients, serving as a significant diagnostic marker for infectious renal disease. Renal ultrasound exhibits lower sensitivity for detecting infectious renal disease compared to contrast-enhanced CT or MRI[ 20 ]. In our cohort, the sensitivity of ultrasound was 40.4% (61/151), exceeding the 25% reported in a previous study[ 14 ]. The lower sensitivity may be attributed to the early stages of abscess formation or their similarity to localized bacterial nephritis, as detection relies on factors such as abscess size, maturity, and debris composition[ 21 ]. The application of contrast-enhanced CT or MRI at our center improved diagnostic accuracy, thereby contributing to these findings. The prevalence of VUR varies from 52.6% in our cohort to 69.2% in a prior study [ 17 ], highlighting the substantial influence of congenital abnormalities in increasing susceptibility to ascending urinary tract infections. The findings endorse the recommendation for post-infection VCUG to evaluate VUR and engage clinical management. Nonetheless, the estimate may be affected by the incomplete VCUG data, with 44.9% not performed. In our cohort, all cases were diagnosed using enhanced CT/MRI, indicating a notable divergence from prior studies[ 6 , 15 , 16 ]. This approach enhances the reliability of renal abscess diagnosis within our cohort, thereby increasing the accuracy of the findings from our study. This study is the first to emphasize the significance of the CT value difference in differentiating renal abscesses. A low CT value difference of 28.8 ± 8.0 HU was observed, potentially indicating a significant finding. This finding might be useful as a significant diagnostic tool for the identification of abscess lesions, especially in cases of abnormal ultrasound results. Additionally, it may decrease diagnostic delays, providing a more dependable and efficient diagnostic method. Several limitations restrict the generalizability and depth of these findings. The single-center design at a tertiary hospital may introduce selection bias, as the cohort may overrepresent severe or referred cases, potentially leading to an underestimating of milder community presentations. The sample size of 69 patients, while the largest cohort of pediatric renal abscesses, may restrict statistical power and the capacity to make strong causal inferences, especially among varying age groups. The retrospective design may introduce potential biases that could compromise the reliability of historical trends. The incomplete VCUG performance likely underestimates the actual prevalence of VUR, given that only 38 patients were evaluated. The low positivity rates of blood and urine cultures may be attributed to prior antibiotic administration before sampling. This may disrupt the characterization of pathogen distribution. The lack of long-term follow-up data limits the ability to assess recurrence rates, chronic renal function, and the effects of VUR on long-term outcomes. This study presents multiple opportunities for future research to tackle unanswered questions and improve clinical practice. The CT value findings—minimum of 20.7 ± 7.6 HU and a difference of 28.8 ± 8.0 HU—require further validation as diagnostic biomarkers in larger cohorts, with the potential to establish standardized thresholds for enhancing abscess detection. These findings may assist in differentiating renal abscesses from ABFN. Multicenter prospective studies are crucial for validating the elevated prevalence of enterococcus and examining regional disparities in microbial resistance. This research may contribute to the development of customized antibiotic guidelines and help mitigate the low culture positivity rates. Long-term follow-up studies are essential for evaluating recurrence risks, renal function outcomes, and the prognostic implications of VUR, thereby ensuring comprehensive care for this at-risk population. Conclusion This study evaluates the clinical profile of renal abscesses in a substantial cohort of pediatric patients. The research emphasized the significance of CT value variations (28.8 ± 8.0 HU) in differentiating renal abscesses. The significant prevalence of VUR justifies the recommendation for post-infection VCUG to evaluate VUR and guide clinical management strategies. Furthermore, Enterococcus species have emerged as a notable pathogen within our cohort, indicating the need for further investigation into regional microbial resistance patterns. Declarations Ethical Approval This retrospective study was approved by the Institutional Review Board of Shenzhen Children’s Hospital (Approval No. SZCH-IRB-2025006), and written informed consent was obtained from the parents or legal guardians of all participants. Conflict of Interest The authors declare that the research was conducted without any commercial or financial relationships that could be construed as potential conflicts of interest. Author Contributions J.G. and M.G. collaboratively drafted the manuscript and made equal contributions to the article. S.J. and Y.M. conducted the collection and analysis of clinical data and prepared the figures. X.G. and J. Li served as the corresponding authors and were accountable for the critical revision of the manuscript. All authors have conducted a review and granted approval for the final manuscript. Funding This study was supported by the Guangdong High-Level Hospital Construction Fund. Availability of data and material The datasets produced and analyzed in this study are accessible from the corresponding author upon reasonable request. Acknowledgments We express our gratitude to the clinical staff at Shenzhen Children's Hospital for their essential contributions to patient management and data collection. References Moore CA, Gangai MP (1967) Renal cortical abscess. J Urol 98:303–306. https://doi.org/10.1016/S0022-5347(17)62875-1 Uehling DT, Hahnfeld LE, Scanlan KA (2000) Urinary tract abnormalities in children with acute focal bacterial nephritis. BJU Int 85:885–888. https://doi.org/10.1046/j.1464-410x.2000.00622.x Bitsori M, Raissaki M, Maraki S, Galanakis E (2015) Acute focal bacterial nephritis, pyonephrosis and renal abscess in children. 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JAMA 256:895–899 Cite Share Download PDF Status: Published Journal Publication published 27 Mar, 2026 Read the published version in Pediatric Nephrology → Version 1 posted Editorial decision: Major Revisions Needed 21 Sep, 2025 Reviewers agreed at journal 08 Sep, 2025 Reviewers invited by journal 08 Sep, 2025 Editor assigned by journal 08 Sep, 2025 First submitted to journal 03 Sep, 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-7531142","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":511818708,"identity":"b308e33f-44a8-444e-8a12-a17354493a10","order_by":0,"name":"Jian-Qun Guo","email":"","orcid":"","institution":"Shenzhen Children's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Jian-Qun","middleName":"","lastName":"Guo","suffix":""},{"id":511818709,"identity":"cf2b10a8-7663-4276-ae6f-2e993043e5c2","order_by":1,"name":"Mei-Hao Gao","email":"","orcid":"","institution":"The University of Hong Kong-Shenzhen Hospital","correspondingAuthor":false,"prefix":"","firstName":"Mei-Hao","middleName":"","lastName":"Gao","suffix":""},{"id":511818710,"identity":"b1480c97-2d51-4d50-b77c-c0be1d09c8a7","order_by":2,"name":"Yi-Jiao Ma","email":"","orcid":"","institution":"Shenzhen Children's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yi-Jiao","middleName":"","lastName":"Ma","suffix":""},{"id":511818711,"identity":"711ec4ba-9344-4ae6-a52a-1c9276534e82","order_by":3,"name":"Shi-Lei Jia","email":"","orcid":"","institution":"Shenzhen Children's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Shi-Lei","middleName":"","lastName":"Jia","suffix":""},{"id":511818712,"identity":"9d9cd2b5-ce9e-4d05-b95c-29f7feb2e120","order_by":4,"name":"Xiao-Jie Gao","email":"","orcid":"","institution":"Shenzhen Children's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Xiao-Jie","middleName":"","lastName":"Gao","suffix":""},{"id":511818713,"identity":"038bea5f-3c35-4008-8024-322f0672056d","order_by":5,"name":"Jun Li","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA60lEQVRIiWNgGAWjYBACNvbm4z8+/rGp3z//8MEHCRU1hLXw8RxLkJzZkMa4QYIt2eDBmWOEtchJ5ChIczYcBmrhMZN82MJMhMN4zjAYM+44zGwu3WBWkdjAxsDf3p1AwC+9B5ILz6SzWc45kHYjcYcMg8SZsxsI2HIu4fAMNmsehgMJx24knmFjMJDIJaBFIsewmYeNWYLhQGJbQWIbM1FajJl525wNDG4kszEQp4XnWBrjjDNpCZI9x5glEs4c4yHoF/n25mMMHypsEvjZ+z9+/FFRI8ff3otfCwbgIU35KBgFo2AUjAKsAACVFEz9RmS3aAAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0001-7856-4402","institution":"Shenzhen Children's Hospital","correspondingAuthor":true,"prefix":"","firstName":"Jun","middleName":"","lastName":"Li","suffix":""}],"badges":[],"createdAt":"2025-09-04 02:17:53","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7531142/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7531142/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00467-025-07114-4","type":"published","date":"2026-03-27T16:12:39+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":91487504,"identity":"95d1b1e4-e399-4702-9fc6-0d0fd462ec36","added_by":"auto","created_at":"2025-09-17 05:03:14","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":322186,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSize of renal abscess and related clinical data.\u003c/strong\u003e\u003cbr\u003e\n \u003cstrong\u003e(A)\u003c/strong\u003e Three-dimensional scatter plot representing the renal abscess size in three different dimensions: Craniocaudal (CC), Transverse (TR), and Anteroposterior (AP).\u003cbr\u003e\n \u003cstrong\u003e(B)\u003c/strong\u003e Distribution of urine culture results in 69 patients, with 24 positive results, including one case with a Gram-negative bacterium, where the species was not identified due to insufficient bacterial growth following antibiotic treatment.\u003cbr\u003e\n \u003cstrong\u003e(C-E)\u003c/strong\u003e Comparison of renal abscess dimensions between left kidney (19 of 32 cases with documented dimensions data) and right kidney (11 of 30 cases with documented dimensions data) across CC, TR, and AP dimensions.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eF.\u003c/strong\u003e Differences in hospital stay duration across three age groups: 1–24 months, 25–60 months, and \u0026gt;60 months.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e(G)\u003c/strong\u003e Imaging features of renal abscesses on plain and contrast-enhanced CT, with blue arrows marking CT changes.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e(H)\u003c/strong\u003e MRI images highlighting abscesses with red arrows.\u003c/p\u003e\n\u003cp\u003eNotes:\u003c/p\u003e\n\u003cp\u003eCraniocaudal (CC): Longitudinal length measured from the upper pole to the lower pole of the kidney.\u003c/p\u003e\n\u003cp\u003eTransverse (TR): Lateral width measured perpendicular to the craniocaudal axis (left-to-right direction).\u003c/p\u003e\n\u003cp\u003eAnteroposterior (AP): Thickness measured along the anterior-posterior axis (abdominal depth from ventral to dorsal surface).\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7531142/v1/05d1564d562647a3d5163366.png"},{"id":105756073,"identity":"d18e6be4-9209-4839-9fcb-226ed20f5990","added_by":"auto","created_at":"2026-03-30 16:35:13","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1165445,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7531142/v1/4fa18025-57ce-4b6f-a36b-79b3fdf3d529.pdf"}],"financialInterests":"","formattedTitle":"Pediatric Renal Abscess: A 12-year Single-Center Retrospective Analysis","fulltext":[{"header":"Introduction","content":"\u003cp\u003eRenal abscesses are localized accumulations of purulent fluid within the kidneys, representing a rare but severe complication of urinary tract infections (UTIs) [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. They generally emerge not as distinct entities but as a continuum from acute focal bacterial nephritis (AFBN) or persistent UTIs. The fundamental pathology includes significant vasospasm, inflammation, and liquefactive necrosis. The incidence of renal abscesses remains unclear. Improvements in imaging technologies, especially contrast-enhanced computed tomography (CT) or magnetic resonance imaging (MRI), have markedly enhanced detection rates[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Nevertheless, timely diagnosis remains challenging due to the nonspecific nature of symptoms, which often overlap with those of common UTIs. Early detection and intervention are critical to prevent severe consequences such as renal impairment or sepsis[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIn pediatric patients, renal abscesses are frequently attributed to congenital abnormalities of the urinary tract, including vesicoureteral reflux (VUR), structural ureter and bladder anomalies, and duplicated renal systems[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. These conditions predispose children to recurrent infections that may progress to abscess formation. Bacteremia can also contribute to abscess formation. The incidence of renal abscesses caused by Streptococcus has decreased due to advancements in vaccination and antibiotics. However, Escherichia coli and other gram-negative bacteria have emerged as the main pathogens[\u003cspan additionalcitationids=\"CR8\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Notably, the emerging role of Enterococcus species as a causative agent, particularly in regions with distinct resistance patterns, remains inadequately explored, highlighting a significant knowledge gap.\u003c/p\u003e\u003cp\u003eThe existing literature on renal abscesses exhibits several limitations. Studies often focus on general disease aspects, neglecting important factors such as age-specific traits and the comparative diagnostic effectiveness of imaging techniques. Additionally, limited sample sizes in numerous studies compromise the strength and applicability of results. Ultrasound, commonly employed for initial screening in diagnostics, exhibits limited accuracy, particularly for small or early-stage abscesses. While contrast-enhanced CT and MRI offer more reliable diagnostic tools, the establishment of standardized diagnostic threshold (e.g., specific CT value differences) for abscess identification remain undefined.\u003c/p\u003e\u003cp\u003eOne area of uncertainty pertains to the role of VUR. The prevalence of VUR in children with renal abscesses, despite being acknowledged as a risk factor, remains inadequately defined. Consequently, a consensus on the necessity of routine post-infection voiding cystourethrogram (VCUG) for evaluating VUR in this population remains absent. The existing knowledge gaps contribute to an inadequately defined clinical profile and diagnostic strategy for renal abscesses in pediatric patients. This study investigates the clinical and etiological characteristics of renal abscesses in children, focusing on age-specific characteristics, microbial pathogen distribution, and imaging and laboratory findings. This study aims to rectify existing deficiencies and enhance the understanding of pediatric renal abscesses within this particular population.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003eStudy Design\u003c/p\u003e\u003cp\u003eThe research enrolled 69 patients diagnosed with renal abscesses at Shenzhen Children\u0026rsquo;s Hospital in Guangdong Province, China, from November 2012 to February 2024. Out of 151 cases initially screened for suspected renal abscesses, 69 were confirmed eligible after evaluation with contrast-enhanced CT or MRI. All patients received initial renal ultrasound screening to detect potential abnormalities. The inclusion criteria required a definitive diagnosis through contrast-enhanced CT or MRI. Renal abscesses were characterized as: (1) on contrast-enhanced CT, well-defined hypodense lesions (typically 0\u0026ndash;20 Hounsfield Units) with rim enhancement and often accompanied by perinephric fat stranding or fluid collections[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]; or (2) on MRI, lesions exhibiting T2-hyperintensity, T1-hypointensity, rim enhancement on post-contrast T1-weighted imaging, and restricted diffusion on diffusion-weighted imaging (DWI) with low apparent diffusion coefficient (ADC) values[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Cases diagnosed exclusively through renal ultrasound were excluded because of its lower sensitivity and specificity in confirming renal abscesses.\u003c/p\u003e\u003cp\u003eData Collection\u003c/p\u003e\u003cp\u003ePatients were categorized into three age groups according to developmental and clinical relevance: (1) infants and toddlers (1\u0026ndash;24 months), (2) preschool children (25\u0026ndash;60 months), and (3) school-age children (\u0026gt;\u0026thinsp;60 months). Demographic data, clinical symptoms, imaging findings, and laboratory results were obtained from electronic medical records. Structural urinary abnormalities were evaluated through renal ultrasound, contrast-enhanced CT/MRI, or VCUG.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eStatistical Analysis\u003c/h2\u003e\u003cp\u003eContinuous variables were summarized as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (SD) for normally distributed data and median with interquartile range (IQR) for non-normally distributed data, as assessed by the Shapiro-Wilk test. The Student\u0026rsquo;s t-test was utilized for pairwise comparisons of normally distributed data, whereas the Mann-Whitney U test was employed for non-normally distributed data. One-way analysis of variance (ANOVA) was utilized for normally distributed data in multiple group comparisons, while the Kruskal-Wallis test was applied for non-normally distributed data. Categorical variables were assessed through the Chi-square test or Fisher\u0026rsquo;s exact test when expected cell counts were less than 5. The Bonferroni correction was utilized to account for multiple comparisons. A two-tailed P-value of less than 0.05 was deemed statistically significant. Data analysis was conducted utilizing GraphPad Prism version 9.5.0.\u003c/p\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003eClinical Characteristic\u003c/h2\u003e\u003cp\u003eThe study comprised 69 patients diagnosed with renal abscesses, exhibiting a median age of 24 months (interquartile range [IQR]: 7.3, 66.8 months) and a male-to-female ratio of 35:34. Age-stratified analysis indicated a male predominance in the 1\u0026ndash;24-month age group (26 males compared to 9 females), while females were predominated in the \u0026gt;\u0026thinsp;60-month age group (17 females compared to 2 males). In terms of abscess location, left-sided abscesses were identified in 32 patients (46.4%), right-sided abscesses in 30 patients (43.5%), and bilateral abscesses in 7 patients (10.1%). The most common clinical manifestations include fever, present in 98.6% of patients (68/69), followed by gastrointestinal symptoms (vomiting, diarrhea, and nausea) in 26.1% (18/69) and abdominal pain in 29.0% (20/69). Infrequent symptoms were reported, including loin pain in 5.8% (4/69), abdominal distension in 1.4% (1/69), and respiratory symptoms in 14.5% (10/69). Neurological manifestations occurred in 5.8% of cases (4/69), whereas urinary smell and oliguria were each observed in 1.4% (1/69). Furthermore, 20.3% of patients (14/69) experienced recurrent urinary tract infections (UTIs), whereas 5.8% (4/69) had a documented history of fever of unknown origin, as presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eDemographic and clinical characteristics of pediatric patients with renal abscesses, stratified by age group.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariables\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAll patients\u003c/p\u003e\u003cp\u003e(N\u0026thinsp;=\u0026thinsp;69)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1\u0026ndash;24 months\u003c/p\u003e\u003cp\u003e(N\u0026thinsp;=\u0026thinsp;35)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e25\u0026ndash;60 months\u003c/p\u003e\u003cp\u003e(N\u0026thinsp;=\u0026thinsp;15)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;60 months\u003c/p\u003e\u003cp\u003e(N\u0026thinsp;=\u0026thinsp;19)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eP value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGender\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.0001\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMale\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e50.7% (35/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e74.3% (26/35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e46.7% (7/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e10.5% (2/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFemale\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e49.3% (34/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e25.7% (9/35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e53.3% (8/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e89.5% (17/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eAge-Group distribution\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e100% (69/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e50.7% (35/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e21.7% (15/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e27.6% (19/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eMedian age (months)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e24.0\u003c/p\u003e\u003cp\u003e(IQR: 7.3\u0026ndash;66.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.3\u003c/p\u003e\u003cp\u003e(IQR: 4.0\u0026ndash;9.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e43.4\u003c/p\u003e\u003cp\u003e(IQR: 36.0-53.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e90.0\u003c/p\u003e\u003cp\u003e(IQR: 78.1\u0026ndash;106.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.0001\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eAbscess location\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e\u003cb\u003e0.942\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLeft kidney\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e46.4% (32/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e45.7% (16/35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e46.7% (7/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e47.4% (9/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRight kidney\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e43.5% (30/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e42.9% (15/35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e40.0% (6/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e47.4% (9/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBilateral\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10.1% (7/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e11.4% (4/35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e13.3% (2/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e5.2% (1/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eRecurrent infection\u003c/b\u003e*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e26.1% (18/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e37.1% (13/35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e6.7% (1/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e21.5% (4/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e\u003cb\u003e0.045\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eHospital stays (days)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e12.0\u003c/p\u003e\u003cp\u003e(IQR: 9.0\u0026ndash;15.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e12.0\u003c/p\u003e\u003cp\u003e(IQR: 9.0-15.6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e14.0\u003c/p\u003e\u003cp\u003e(IQR: 10.5\u0026ndash;15.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e11.0\u003c/p\u003e\u003cp\u003e(IQR: 9.5\u0026ndash;13.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e\u003cb\u003e0.3723\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eSymptoms\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFever\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e98.6% (68/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e97.1% (34/35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e100.0% (15/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e100.0% (19/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAbdominal pain\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e29.0% (20/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003csup\u003e\u0026dagger;\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e53.3% (8/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e63.2% (12/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVomiting and diarrhea\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e26.1% (18/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e11.4% (4/35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e53.3% (8/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e31.6% (6/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCough and runny nose\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e14.5% (10/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e20.0% (7/35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e6.7% (1/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e10.5% (2/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLoin pain\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e5.8% (4/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003csup\u003e\u0026dagger;\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e6.7% (1/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e15.8% (3/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAbdominal distension\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.4% (1/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003csup\u003e\u0026dagger;\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.0% (0/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e5.3% (1/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDysuria\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e5.8% (4/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.9% (1/35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.0% (0/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e15.8% (3/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eUltrasound abnormalities\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eEnlarged kidney\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e52.2% (36/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e48.6% (17/35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e60.0% (9/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e52.6% (10/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e\u003cb\u003e0.75\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHydronephrosis\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e29.0% (20/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e40.0% (14/35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e13.3% (2/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e21.1% (4/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e\u003cb\u003e0.089\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eUreteral dilation\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e13.0% (9/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e22.9% (8/35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.0% (0/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e5.3% (1/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e\u003cb\u003e0.023\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDuplicated system\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4.3% (3/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.0% (0/35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e13.3% (2/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e5.3% (1/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e\u003cb\u003e0.091\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eVUR Detection\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e52.6% (20/38)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e62.5% (15/24)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e16.7% (1/6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e50.0% (4/8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e\u003cb\u003e0.042\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eElevated markers\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBlood WBC\u003csup\u003e\u0026Dagger;\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e65.2% (45/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e62.9% (22/35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e66.7% (10/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e68.4% (13/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e\u003cb\u003e0.895\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBlood CRP\u003csup\u003e\u0026Dagger;\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e85.5% (59/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e82.9% (29/35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e93.3% (14/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e84.2% (16/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e\u003cb\u003e0.674\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eUrine WBC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e78.3% (54/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e85.7% (30/35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e46.8% (7/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e89.5% (17/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e\u003cb\u003e0.005\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eUrine RBC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e39.1% (27/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e31.4% (11/35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e46.8% (7/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e47.4% (9/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e\u003cb\u003e0.379\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eUrine LE\u003csup\u003e\u0026sect;\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e59.4% (41/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e71.4% (25/35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e33.3% (5/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e57.9% (11/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e\u003cb\u003e0.022\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eTreatment outcomes\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSurgical intervention \u003csup\u003e\u0026para;\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7.2% (5/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5.7% (2/35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e13.3% (2/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e5.3% (1/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e\u003cb\u003e0.615\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAcute kidney injury \u003csup\u003e#\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7.2% (5/69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e11.4% (4/35)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e6.7% (1/15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.0% (0/19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e\u003cb\u003e0.246\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"6\"\u003eNotes:\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"6\"\u003e* represents cases with recurrent urinary tract infections and recurrent fever of unknown origin.\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"6\"\u003e\u0026dagger; indicates that patients under 24 months of age are often unable to express feelings of abdominal pain or loin pain or abdominal distension.\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"6\"\u003e\u0026Dagger; denotes elevated with white blood cell count (WBC\u0026thinsp;\u0026gt;\u0026thinsp;15 \u0026times; 10⁹/L) or C-reactive protein (CRP\u0026thinsp;\u0026gt;\u0026thinsp;30 mg/L).\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"6\"\u003e\u0026sect; represents Leukocyte Esterase (LE), a urinary marker of infection.\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"6\"\u003e\u0026para; refers to surgical intervention, defined as drainage or surgical procedures for renal abscesses.# indicates acute kidney injury (AKI), classified according to the pRIFLE (Pediatric Risk, Injury, Failure, Loss, End Stage Renal Disease) criteria.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eImaging Findings\u003c/p\u003e\u003cp\u003eUltrasound detected urinary tract abnormalities in approximately half of the cases, with enlarged kidneys in 52.2% (36/69), hydronephrosis in 29.0% (20/69), ureteral dilation in 13.0% (9/69), and duplicated collecting systems in 4.3% (3/69) (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Among these 69 patients, 8 exhibited normal renal ultrasound findings at presentation, subsequently confirmed as renal abscesses by enhanced CT or MRI, resulting in an ultrasound sensitivity of 40.4% (61/151). Imaging modalities included enhanced CT in 64 patients (92.8%, 64/69) and enhanced renal MRI in 8 patients (11.6%, 8/69), with 3 patients receiving both procedures simultaneously. The minimum CT value in the abscess area was 20.7\u0026thinsp;\u0026plusmn;\u0026thinsp;7.6 Hounsfield Units (HU) in 35 of the 69 patients with documented CT values in radiology reports. The CT value difference between the abscess area and adjacent normal tissue was 28.8\u0026thinsp;\u0026plusmn;\u0026thinsp;8.0 HU in 37 of the 69 patients with documented CT value differences in radiology reports. Analysis of abscess diameters in the left (n\u0026thinsp;=\u0026thinsp;19) and right (n\u0026thinsp;=\u0026thinsp;11) kidneys indicated significantly larger diameters in the left kidney for the craniocaudal (CC) dimension (23.93\u0026thinsp;\u0026plusmn;\u0026thinsp;11.79 mm vs. 12.76\u0026thinsp;\u0026plusmn;\u0026thinsp;5.58 mm; P\u0026thinsp;=\u0026thinsp;0.0065) and anteroposterior (AP) dimension (21.16\u0026thinsp;\u0026plusmn;\u0026thinsp;8.69 mm vs. 12.55\u0026thinsp;\u0026plusmn;\u0026thinsp;4.65 mm; P\u0026thinsp;=\u0026thinsp;0.0052). No significant difference was observed in the transverse (TR) dimension (19.65\u0026thinsp;\u0026plusmn;\u0026thinsp;8.76 mm vs. 13.69\u0026thinsp;\u0026plusmn;\u0026thinsp;5.91 mm; P\u0026thinsp;=\u0026thinsp;0.0552) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA and \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eC). Of the 69 patients, 44.9% (31/69) refused VCUG, which restricts the evaluation of VUR. Among the 38 patients who underwent VCUG, 52.6% (20/38) were diagnosed with VUR, of which 45.0% (9/20) exhibited bilateral involvement (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Age-stratified analysis of VCUG results indicated that VUR were present in 62.5% (15/24) of the 1\u0026ndash;24-month group, 16.7% (1/6) of the 25\u0026ndash;60-month group, and 50.0% (4/8) of the \u0026gt;\u0026thinsp;60-month group. Additionally, 11, 9, and 11 patients from each respective group did not undergo VCUG. Three patients present with distinct conditions: one exhibits bilateral vesicoureteral reflux (VUR), megaureter, and left ureteropelvic junction stenosis (UPJO); another has right-sided Grade III VUR, megaureter, ureteral diverticulum, and neurogenic bladder; and the third is diagnosed with left ureteral segmental stenosis via intravenous pyelogram (IVP).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eGrading distribution of vesicoureteral reflux (VUR) detected by voiding cystourethrography (VCUG) in the evaluated pediatric renal abscess cohort.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCategory\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFrequency(n)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePercentage (%)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVCUG Assessment Status\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eUnassessed\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e44.9% (31/69)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eEvaluated\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e38\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e55.1% (38/69)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eVUR Diagnosis (N\u0026thinsp;=\u0026thinsp;38)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNo VUR detected\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e47.4% (18/38)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVUR present\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e52.6% (20/38)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLeft VUR\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- Left Grade II\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.6% (1/38)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- Left Grade III\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e13.2% (5/38)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- Left Grade IV\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.6% (1/38)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRight VUR\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- Right Grade III\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e7.9% (3/28)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- Right Grade IV\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.6% (1/38)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBilateral VUR\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- Right Grade I, Left Grade V\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.6% (1/38)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- Right Grade II, Left Grade II\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.6% (1/38)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- Right Grade III, Left Grade I\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e5.3% (2/38)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- Right Grade III, Left Grade II\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e5.3% (2/38)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- Right Grade III, Left Grade III\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e5.3% (2/38)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- Right Grade IV, Left Grade III\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.6% (1/38)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eLaboratory Findings:\u003c/p\u003e\u003cp\u003eMost of the 69 patients exhibited elevated systemic inflammation markers. C-reactive protein was elevated in 85.5% (59/69) of cases, blood leukocytosis was observed in 65.2% (45/69), urine white blood cells were present in 78.3% (54/69), urine red blood cells were found in 39.1% (27/69), and leukocyte esterase was detected in 59.4% (41/69). Urine cultures revealed pathogens in 34.8% of cases (24/69). Escherichia coli was identified in 37.5% (9/24) of these instances, followed by Enterococcus species at 25.0% (6/24), Enterobacter cloacae at 8.3% (2/24), Klebsiella species at 4.2% (1/24), Candida glabrata at 4.2% (1/24), and Corynebacterium glucuronolyticum at 4.2% (1/24). One patient identified an unclassified Gram-negative bacterium with a low count attributed to prior antibiotic administration. Blood cultures were performed in 66 out of 69 patients. The results were positive in 3.0% (2/66), identifying Klebsiella pneumoniae and Streptococcus constellatus. Purulent fluid cultures from renal abscesses in two patients were positive for Klebsiella pneumoniae and Streptococcus constellatus.\u003c/p\u003e\u003cp\u003eTreatment Outcomes\u003c/p\u003e\u003cp\u003eAll 69 patients were administered empirical antibiotic therapy. Surgical intervention, including drainage or nephrectomy, was required in 7.2% of cases (5/69) due to the progression of abscesses or perirenal extension. Acute kidney injury (AKI) was also observed in 7.2% of patients (5/69), with resolution achieved through conservative management within 4 weeks. The median duration of hospital stay was 12.0 days (interquartile range [IQR]: 9.0, 15.0 days), with no statistically significant difference observed among the three age groups (P\u0026thinsp;=\u0026thinsp;0.3723) (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). However, patients with left-sided or bilateral kidney involvement had a longer hospital stay than those with right-sided kidney involvement, with statistically significant differences (adjusted P\u0026thinsp;=\u0026thinsp;0.0315 for left-sided, P\u0026thinsp;=\u0026thinsp;0.0327 for bilateral).\u003c/p\u003e\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eRenal abscess, a rare but serious inflammatory condition characterized by purulent collections within the renal parenchyma. Diagnosis has historically been difficult due to limited imaging techniques, often resulting in delayed recognition, extended hospitalization or the need for invasive procedures[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Recent advancements in antimicrobial therapy and imaging technologies, including contrast-enhanced CT and MRI, have improved detection rates. Nonetheless, renal abscesses continue to be underrecognized in clinical practice, especially in pediatric populations[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. This retrospective study from a single center constitutes the largest cohort of pediatric renal abscess cases reported to date. The aim was to outline the clinical, diagnostic, and therapeutic characteristics of renal abscesses in pediatric patients.\u003c/p\u003e\u003cp\u003eFever was noted in almost all patients within our cohort. Furthermore, 20.3% (14/69) exhibited a history of recurrent urinary tract infections, while 5.8% (4/69) presented with recurrent fever of unknown origin. These findings are consistent with prior research[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] and indicate a more robust association between recurrent UTIs and the development of renal abscesses. Our cohort demonstrated no significant gender difference in pediatric renal abscesses, which contrasts with previous studies indicating a female predominance[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Age stratification revealed a male predominance in infants (26 vs. 9, 1\u0026ndash;24 months) and a female predominance in older children (17 vs. 2, \u0026gt;\u0026thinsp;60 months). The findings correspond with gender-specific patterns of UTIs, indicating that renal abscesses are predominantly a result of ascending infections. Renal abscesses may develop on either side of the kidney; however, our study suggests a higher prevalence of unilateral involvement. Nonetheless, no significant difference was observed between left- and right-sided involvement, which contradicts earlier studies indicating a higher incidence of right-sided abscesses[\u003cspan additionalcitationids=\"CR15\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. The finding that patients with left-sided or bilateral renal abscesses had longer hospital stays than those with right-sided involvement indicates possible variations in disease severity or management difficulties. This finding may indicate anatomical complexity or larger abscess volumes on the left side, as evidenced by significant diameter differences in the craniocaudal and anteroposterior dimensions, potentially requiring prolonged antibiotic therapy or increased monitoring for surgical intervention. This suggests a potential benefit in customizing treatment duration and monitoring intensity based on abscess location and size, an area warranting further investigation. The urine culture positivity rate of 34.8% is considerably lower than findings in earlier studies[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], probably attributable to prior antibiotic administration before admission. This also indirectly highlights the problem of inappropriate antibiotic use in Shenzhen, specifically the lack of culture specimen collection prior to antibiotic administration. The prevalence of gram-negative pathogens, notably Escherichia coli (37.5%), indicates that initial empirical antibiotic therapy should focus on this group, while also considering Enterococcus species (25.0%) in the context of local resistance patterns. The incidence of Enterococcus species notably surpasses findings from other pediatric cohorts[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], which may indicate regional variations in antibiotic usage, microbial resistance, or healthcare practices.\u003c/p\u003e\u003cp\u003eUltrasound serves as a basic screening method for renal abscesses, unaffected by impaired renal function or complications arising from contrast material allergies[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Renal enlargement identified via ultrasound was observed in 52.2% (36/69) of patients, serving as a significant diagnostic marker for infectious renal disease. Renal ultrasound exhibits lower sensitivity for detecting infectious renal disease compared to contrast-enhanced CT or MRI[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. In our cohort, the sensitivity of ultrasound was 40.4% (61/151), exceeding the 25% reported in a previous study[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. The lower sensitivity may be attributed to the early stages of abscess formation or their similarity to localized bacterial nephritis, as detection relies on factors such as abscess size, maturity, and debris composition[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. The application of contrast-enhanced CT or MRI at our center improved diagnostic accuracy, thereby contributing to these findings. The prevalence of VUR varies from 52.6% in our cohort to 69.2% in a prior study [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], highlighting the substantial influence of congenital abnormalities in increasing susceptibility to ascending urinary tract infections. The findings endorse the recommendation for post-infection VCUG to evaluate VUR and engage clinical management. Nonetheless, the estimate may be affected by the incomplete VCUG data, with 44.9% not performed.\u003c/p\u003e\u003cp\u003eIn our cohort, all cases were diagnosed using enhanced CT/MRI, indicating a notable divergence from prior studies[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. This approach enhances the reliability of renal abscess diagnosis within our cohort, thereby increasing the accuracy of the findings from our study. This study is the first to emphasize the significance of the CT value difference in differentiating renal abscesses. A low CT value difference of 28.8\u0026thinsp;\u0026plusmn;\u0026thinsp;8.0 HU was observed, potentially indicating a significant finding. This finding might be useful as a significant diagnostic tool for the identification of abscess lesions, especially in cases of abnormal ultrasound results. Additionally, it may decrease diagnostic delays, providing a more dependable and efficient diagnostic method.\u003c/p\u003e\u003cp\u003eSeveral limitations restrict the generalizability and depth of these findings. The single-center design at a tertiary hospital may introduce selection bias, as the cohort may overrepresent severe or referred cases, potentially leading to an underestimating of milder community presentations. The sample size of 69 patients, while the largest cohort of pediatric renal abscesses, may restrict statistical power and the capacity to make strong causal inferences, especially among varying age groups. The retrospective design may introduce potential biases that could compromise the reliability of historical trends. The incomplete VCUG performance likely underestimates the actual prevalence of VUR, given that only 38 patients were evaluated. The low positivity rates of blood and urine cultures may be attributed to prior antibiotic administration before sampling. This may disrupt the characterization of pathogen distribution. The lack of long-term follow-up data limits the ability to assess recurrence rates, chronic renal function, and the effects of VUR on long-term outcomes.\u003c/p\u003e\u003cp\u003eThis study presents multiple opportunities for future research to tackle unanswered questions and improve clinical practice. The CT value findings\u0026mdash;minimum of 20.7\u0026thinsp;\u0026plusmn;\u0026thinsp;7.6 HU and a difference of 28.8\u0026thinsp;\u0026plusmn;\u0026thinsp;8.0 HU\u0026mdash;require further validation as diagnostic biomarkers in larger cohorts, with the potential to establish standardized thresholds for enhancing abscess detection. These findings may assist in differentiating renal abscesses from ABFN. Multicenter prospective studies are crucial for validating the elevated prevalence of enterococcus and examining regional disparities in microbial resistance. This research may contribute to the development of customized antibiotic guidelines and help mitigate the low culture positivity rates. Long-term follow-up studies are essential for evaluating recurrence risks, renal function outcomes, and the prognostic implications of VUR, thereby ensuring comprehensive care for this at-risk population.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis study evaluates the clinical profile of renal abscesses in a substantial cohort of pediatric patients. The research emphasized the significance of CT value variations (28.8\u0026thinsp;\u0026plusmn;\u0026thinsp;8.0 HU) in differentiating renal abscesses. The significant prevalence of VUR justifies the recommendation for post-infection VCUG to evaluate VUR and guide clinical management strategies. Furthermore, Enterococcus species have emerged as a notable pathogen within our cohort, indicating the need for further investigation into regional microbial resistance patterns.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthical Approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis retrospective study was approved by the Institutional Review Board of Shenzhen Children’s Hospital (Approval No. SZCH-IRB-2025006), and written informed consent was obtained from the parents or legal guardians of all participants.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that the research was conducted without any commercial or financial relationships that could be construed as potential conflicts of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eJ.G. and M.G. collaboratively drafted the manuscript and made equal contributions to the article. S.J. and Y.M. conducted the collection and analysis of clinical data and prepared the figures. X.G. and J. Li served as the corresponding authors and were accountable for the critical revision of the manuscript. All authors have conducted a review and granted approval for the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was supported by the Guangdong High-Level Hospital Construction Fund.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and material\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets produced and analyzed in this study are accessible from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe express our gratitude to the clinical staff at Shenzhen Children's Hospital for their essential contributions to patient management and data collection.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eMoore CA, Gangai MP (1967) Renal cortical abscess. J Urol 98:303\u0026ndash;306. https://doi.org/10.1016/S0022-5347(17)62875-1\u003c/li\u003e\n \u003cli\u003eUehling DT, Hahnfeld LE, Scanlan KA (2000) Urinary tract abnormalities in children with acute focal bacterial nephritis. BJU Int 85:885\u0026ndash;888. https://doi.org/10.1046/j.1464-410x.2000.00622.x\u003c/li\u003e\n \u003cli\u003eBitsori M, Raissaki M, Maraki S, Galanakis E (2015) Acute focal bacterial nephritis, pyonephrosis and renal abscess in children. Pediatr Nephrol 30:1987\u0026ndash;1993. https://doi.org/10.1007/s00467-015-3141-3\u003c/li\u003e\n \u003cli\u003eLebowitz RL, Fellows KE, Colodny AH (1977) Renal parenchymal infections in children. Radiol Clin North Am 15:37\u0026ndash;47\u003c/li\u003e\n \u003cli\u003eYen DH, Hu SC, Tsai J, et al (1999) Renal abscess: early diagnosis and treatment. Am J Emerg Med 17:192\u0026ndash;197. https://doi.org/10.1016/s0735-6757(99)90060-8\u003c/li\u003e\n \u003cli\u003eSeguias L, Srinivasan K, Mehta A (2012) Pediatric renal abscess: a 10-year single-center retrospective analysis. Hosp Pediatr 2:161\u0026ndash;166. https://doi.org/10.1542/hpeds.2012-0010\u003c/li\u003e\n \u003cli\u003eFair WR, Higgins MH (1970) Renal abscess. J Urol 104:179\u0026ndash;183. https://doi.org/10.1016/s0022-5347(17)61695-1\u003c/li\u003e\n \u003cli\u003eTimmons JW, Perlmutter AD (1976) Renal abscess: a changing concept. J Urol 115:299\u0026ndash;301. https://doi.org/10.1016/s0022-5347(17)59179-x\u003c/li\u003e\n \u003cli\u003eLevin R, Burbige KA, Abramson S, et al (1984) The diagnosis and management of renal inflammatory processes in children. J Urol 132:718\u0026ndash;721. https://doi.org/10.1016/s0022-5347(17)49839-9\u003c/li\u003e\n \u003cli\u003eKawashima A, Sandler CM, Goldman SM, et al (1997) CT of renal inflammatory disease. Radiographics 17:851\u0026ndash;866; discussion 867-868. https://doi.org/10.1148/radiographics.17.4.9225387\u003c/li\u003e\n \u003cli\u003eGoyal A, Sharma R, Bhalla AS, et al (2013) Diffusion-weighted MRI in inflammatory renal lesions: all that glitters is not RCC! Eur Radiol 23:272\u0026ndash;279. https://doi.org/10.1007/s00330-012-2577-0\u003c/li\u003e\n \u003cli\u003eMoenne-Loccoz JP, Bomsel F, Gatti JM, Prot D (1978) Renal abscess in children. A rare but important radiological diagnosis. Pediatr Radiol 7:150\u0026ndash;154. https://doi.org/10.1007/BF00975438\u003c/li\u003e\n \u003cli\u003eGlaser JH, Caspe W, Koenigsberg M (1984) Medical therapy for suppurative renal infections. Pediatrics 73:726\u0026ndash;728\u003c/li\u003e\n \u003cli\u003eSun J, Shi L, Ye L, Xu Y (2025) Pediatric renal abscess: clinical analysis and literature review. Front Pediatr 13:1407437. https://doi.org/10.3389/fped.2025.1407437\u003c/li\u003e\n \u003cli\u003eChen C-Y, Kuo H-T, Chang Y-J, et al (2016) Clinical assessment of children with renal abscesses presenting to the pediatric emergency department. BMC Pediatr 16:189. https://doi.org/10.1186/s12887-016-0732-5\u003c/li\u003e\n \u003cli\u003eBuschel H, Leung P, Stalewski H, et al (2022) Renal abscesses in children: an 11-year retrospective study and review of the literature. ANZ J Surg 92:3293\u0026ndash;3297. https://doi.org/10.1111/ans.17943\u003c/li\u003e\n \u003cli\u003eHosokawa T, Tanami Y, Sato Y, et al (2023) Association between the imaging characteristics of renal abscess and vesicoureteral reflux. J Infect Chemother 29:937\u0026ndash;941. https://doi.org/10.1016/j.jiac.2023.06.005\u003c/li\u003e\n \u003cli\u003eCheng C-H, Tsai M-H, Su L-H, et al (2008) Renal abscess in children: a 10-year clinical and radiologic experience in a tertiary medical center. Pediatr Infect Dis J 27:1025\u0026ndash;1027. https://doi.org/10.1097/INF.0b013e31817b617b\u003c/li\u003e\n \u003cli\u003eShimizu M, Katayama K, Kato E, et al (2005) Evolution of acute focal bacterial nephritis into a renal abscess. Pediatr Nephrol 20:93\u0026ndash;95. https://doi.org/10.1007/s00467-004-1646-2\u003c/li\u003e\n \u003cli\u003eCraig WD, Wagner BJ, Travis MD (2008) Pyelonephritis: radiologic-pathologic review. Radiographics 28:255\u0026ndash;277; quiz 327\u0026ndash;328. https://doi.org/10.1148/rg.281075171\u003c/li\u003e\n \u003cli\u003eSty JR, Wells RG, Schroeder BA, Starshak RJ (1986) Diagnostic imaging in pediatric renal inflammatory disease. JAMA 256:895\u0026ndash;899\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"pediatric-nephrology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pnep","sideBox":"Learn more about [Pediatric Nephrology](http://link.springer.com/journal/467)","snPcode":"467","submissionUrl":"https://www.editorialmanager.com/pnep/default2.aspx","title":"Pediatric Nephrology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"renal abscess, children, enhanced CT/MRI, vesicoureteral reflux","lastPublishedDoi":"10.21203/rs.3.rs-7531142/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7531142/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e\u003cp\u003eRenal abscesses are infrequent but serious consequences of urinary tract infections in children, frequently manifesting with nonspecific symptoms that might postpone diagnosis. Research on pediatric renal abscesses is limited.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e\u003cp\u003eThis retrospective study investigated 69 children with radiologically verified renal abscesses from November 2012 to February 2024. Patients were categorized into three age groups: 1\u0026ndash;24 months, 25\u0026ndash;60 months, and over 60 months. Clinical features, laboratory and imaging results, and therapy outcomes were assessed.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003eThe median age was 24.0 months (IQR: 7.3, 66.8) and the male-to-female ratio of 35:34. Age-stratified analysis revealed a male predominance in the 1\u0026ndash;24-month group (26 males vs. 9 females) and a female predominance in the \u0026gt;\u0026thinsp;60-month group (17 females vs. 2 males). Fever was noted in 98.6% (68/69), abdominal pain in 29.0% (20/69) and gastrointestinal symptoms in 26.1% (18/69). Ultrasound identified enlarged kidneys in 52.2% (36/69) of cases. The sensitivity of renal ultrasound was 40.4% (61/151). Vesicoureteral reflux was observed in 52.6% (20/38) of cases. Urine cultures demonstrated positive results in 34.8% (24/69) of cases, with Escherichia coli (37.5%, 9/24) and Enterococcus species (25.0%, 6/24) identified as the predominant pathogens. Surgical intervention was required in 7.2% (5/69) of cases, and 7.2% (5/69) developed acute kidney injury. The median duration of hospital stay was 12.0 days (IQR: 9.0, 15.0), with an extension observed in cases of left-sided or bilateral involvement (adjusted P\u0026thinsp;=\u0026thinsp;0.0315, 0.0327).\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e\u003cp\u003eThis study highlights the diagnostic importance of enhanced CT/MRI and the significance role of vesicoureteral reflux in pediatric renal abscesses.\u003c/p\u003e","manuscriptTitle":"Pediatric Renal Abscess: A 12-year Single-Center Retrospective Analysis","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-17 05:03:09","doi":"10.21203/rs.3.rs-7531142/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major Revisions Needed","date":"2025-09-22T03:15:17+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2025-09-08T12:53:37+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-09-08T10:17:04+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-09-08T07:12:26+00:00","index":"","fulltext":""},{"type":"submitted","content":"Pediatric Nephrology","date":"2025-09-03T22:16:06+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"pediatric-nephrology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pnep","sideBox":"Learn more about [Pediatric Nephrology](http://link.springer.com/journal/467)","snPcode":"467","submissionUrl":"https://www.editorialmanager.com/pnep/default2.aspx","title":"Pediatric Nephrology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"e5667518-fe5f-439f-9afe-8896119a3a30","owner":[],"postedDate":"September 17th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-03-30T16:32:20+00:00","versionOfRecord":{"articleIdentity":"rs-7531142","link":"https://doi.org/10.1007/s00467-025-07114-4","journal":{"identity":"pediatric-nephrology","isVorOnly":false,"title":"Pediatric Nephrology"},"publishedOn":"2026-03-27 16:12:39","publishedOnDateReadable":"March 27th, 2026"},"versionCreatedAt":"2025-09-17 05:03:09","video":"","vorDoi":"10.1007/s00467-025-07114-4","vorDoiUrl":"https://doi.org/10.1007/s00467-025-07114-4","workflowStages":[]},"version":"v1","identity":"rs-7531142","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7531142","identity":"rs-7531142","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}