Introduction

Hypospadias, one of the most common congenital genitourinary malformations in male children, requires surgical repair focused on constructing a urethra with adequate length and patency. However, postoperative complications such as urethral stricture, anastomotic fistula, and urinary fistula persist at rates of 10–30%, with inappropriate catheterization depth identified as a critical contributing factor1. Current clinical practice predominantly relies on empirical selection of catheter lengths (e.g.13–15 cm), lacking objective standards based on anatomical parameters. This may lead to malpositioning of the catheter tip: excessive insertion risks bladder mucosal injury and hematuria, while insufficient depth elevates urethral pressure, increasing risks of urinary overflow and pain. Consequently, establishing age-related reference values for urethral length in pediatric populations represents an urgent clinical need for optimizing surgical protocols.

Previous studies have predominantly focused on urethral measurements in adults. However, pediatric urethral length undergoes significant dynamic changes during growth, rendering adult data inapplicable. While Kohler et al.2 reported no significant correlation between urethral length and somatic parameters in adults, our preliminary data revealed strong positive correlations with age, height, and weight in minors. These developmental characteristics underscore the necessity of constructing pediatric-specific reference systems. Although imaging modalities such as MRI and ultrasound enable non-invasive anatomical assessment, their application in children is limited by high costs, compliance requirements, and static measurement biases3,4,5,6. In contrast, intraoperative catheter-based measurement combines precision with clinical feasibility, particularly for perioperative patients requiring indwelling catheters.

Through a large-scale cross-sectional investigation, this study systematically established age-stratified reference values for urethral length in 0–18-year-old males for the first time and innovatively validated their application in catheter selection strategies for hypospadias repair. Results demonstrated that catheterization guided by measured urethral lengths significantly reduced postoperative symptom incidence compared to empirical selection. These findings not only address a critical knowledge gap in developmental urology but also provide quantifiable operational standards for precise urethral reconstruction, offering direct guidance for improving surgical outcomes and minimizing iatrogenic injuries.

Subjects and methods

This study was conducted at Ethics Approval No. EC2023-055 between March 2020 and May 2022. After obtaining informed consent, 501 male children and adolescents aged 0 to 18 years, who required inpatient surgery with indwelling catheters, were enrolled. Exclusion criteria included penile anomalies, hypospadias, penile curvature, prior urethral surgery, delayed puberty, and prostatectomy. To ensure consistency, all measurements were performed by the same examiner under standardized conditions (room temperature: 23–25 °C, controlled lighting).

Urethral and penile lengths were measured simultaneously. The examiner gently stretched the penis to maximal extension and mark the external urethral orifice at a parallel position with the catheter without causing discomfort and depressed the pubic fat. A ruler was placed dorsally along the penis, with one end pressed against the symphysis pubis and the other aligned with the tip of the glans. This measurement was recorded as penile length. Urethral length was determined by measuring the distance from the catheter mark to the beginning of the re-inflated balloon after the catheter is removed.

Participants were stratified into eight age groups: 0–2 years (Group 1), 2–4 years (Group 2), 4–6 years (Group 3), 6–8 years (Group 4), 8–10 years (Group 5), 10–12 years (Group 6), 12–14 years (Group 7), and 14–18 years (Group 8). Age, height, weight, and BMI (weight in kilograms divided by height in meters squared) were recorded for all participants.

Additionally, 47 patients diagnosed with hypospadias and undergoing urethroplasty between 2020 and 2022 were randomly divided into two groups: Group A (n = 24) received a postoperative catheter length of 13–15 cm (empirical), while Group B (n = 23) had catheter lengths determined by measured urethral lengths (95th percentile). Postoperative symptoms such as hematuria, pain, and overflow were monitored and recorded in both groups.

Statistical analyses were performed using GraphPad Prism 8.3. Data are presented as mean ± SD. Descriptive statistics and Spearman’s correlation analysis (two-tailed) were used to evaluate relationships between variables. Kruskal-Wallis one-way ANOVA was employed to analyze penile and urethral lengths across age groups. The Chi-square test was used to compare postoperative symptoms between Groups A and B. A p-value < 0.05 was considered statistically significant.

Informed consent was obtained from the patient and the legal guardian.

Results

The study included 501 male children and adolescents with a mean penile length of 5.2 cm (median: 4.7 cm, SD ± 1.7 cm) and a mean urethral length of 12.8 cm (median: 12 cm, SD ± 3.3 cm). The 5th and 95th percentiles for penile length were 3.5 cm and 8.8 cm, respectively, while for urethral length, they were 9 cm and 19.7 cm, respectively. Descriptive statistics for weight, height, and BMI are presented in Tables 1, 2 and 3.Penile and urethral lengths showed positive correlations with age, weight, height, and BMI (Spearman rho = 0.6115 and 0.8546, 0.6196 and 0.8796, 0.6173 and 0.8665, 0.4818 and 0.6593, respectively; all p < 0.001). Urethral length varied significantly across age groups (p < 0.05), while penile length showed no significant differences between Groups 1 and 2, 2 and 3, and 4 and 5 (p > 0.05), but significant differences between other groups (p < 0.05)(Table 4) .A significant difference in clinical symptoms was observed between Group A (empirical catheter length) and Group B (95th percentile measured catheter length) (Pearson Chi-square X² = 23.436, p < 0.05) (Table 5) and (Pearson Chi-square X² = 23.17, p < 0.0001,Odds ratio = 5.61)(Table 6).

Table 1 Descriptive statistics for data of 501 young males.
Full size table
Table 2 Correlation analysis between age, penis length, urethra length, weight, height and body mass index.
Full size table
Table 3 Penile and urethral dimensions recorded in 501 young males in different age group.
Full size table
Table 4 Multiple comparisons of urethrallength and penilelength in different age groups.
Full size table
Table 5 Chi-square test for clinical symptoms in groups A and B.
Full size table
Table 6 Chi-square test for clinical symptoms in group A and B.
Full size table

Discussion

The male urethra, extending from the bladder to the external urethral meatus, measures approximately 17.5 to 20 cm in adults and 5 to 6 cm in infants. It is anatomically divided into posterior and anterior portions. The posterior urethra spans from the bladder neck to the inferior urogenital diaphragm, while the anterior urethra extends distally to the external meatus. Despite its clinical relevance, there is limited literature on urethral length, likely due to variations in measurement methodologies, ethical considerations, and the clinical significance of this topic.

Currently, several methods are employed to measure urethral length, including non-interventional techniques such as magnetic resonance imaging (MRI) and transperineal ultrasound, as well as interventional methods like cystoscopy and urinary catheterization. Non-interventional approaches, while non-invasive, are associated with high costs, challenges in pediatric patient cooperation, and potential inaccuracies due to the inability to fully extend the penile urethra during imaging. In contrast, interventional methods provide more accurate measurements but carry risks such as urethral injury and infection.

Jeong-ah Ryu and Ersan Altun highlighted that MRI is non-invasive and offers detailed three-dimensional anatomical information about the urethra and surrounding tissues4,6. Brocker’s study demonstrated that diffusion-weighted MRI provides comparable urethral length measurements to introital ultrasound3. Félix Fontaine BSc reported excellent agreement between a simple catheter technique and ultrasound assessment, with minimal bias and clinically acceptable limits of agreement5. In our study, we opted for the catheter method to measure urethral length, as it was deemed more authentic, particularly in patients requiring indwelling catheters. Ethical considerations were paramount, given the sensitive nature of genital research, necessitating informed consent and institutional ethics committee approval.

Our study explored the relationship between urethral length and various body parameters. In children, urethral length showed a significant positive correlation with age, height, weight, and BMI. However, no statistically significant correlations were observed in adults2. These findings underscore the developmental nature of urethral length in pediatric populations.Roberto et al. reported flaccid and stretched penile lengths of 9.0 cm and 12.5 cm, respectively, with penile dimensions highly correlated with height and weight7. Aysu et al. found that stretched penile length increased with age in infants, showing significant correlations with weight, height, and BMI in boys8. Our findings align with these studies, indicating that penile length in minors is positively associated with age, height, weight, and BMI.

Hypospadias, a common congenital malformation of the genitourinary system, often requires surgical intervention9. Urethral length is a critical factor in the success of hypospadias repair. Our study provides reference values for urethral length in children of various age groups, aiding urological surgeons in preoperative planning and postoperative care.Postoperative management frequently involves indwelling catheterization. However, the use of modern catheters with air bladders can lead to complications such as urethral stricture, mucosal injury, or anastomotic fistula formation10. Some clinicians have adopted gastric tubes as an alternative to conventional catheters, though catheterization depth is often determined empirically. Our experience suggests a depth of 13 to 15 cm, but we observed that patients frequently experienced abdominal pain, hematuria, or urethral overflow postoperatively, indicating potential over-insertion of the catheter. This can lead to urine leakage along the urethral space, impairing anastomotic healing, and prolonged contact with the bladder mucosa may cause pain and hematuria.To address these issues, we conducted a comparative study between two groups: Group A (experience-based catheterization depth) and Group B (the 95th percentile of measurement-based catheterization depth ). The results confirmed our hypothesis, with Group A exhibiting significantly higher rates of clinical symptoms compared to Group B (p < 0.05). This underscores the importance of precise catheterization depth based on measured urethral length to minimize postoperative complications.

Conclusion

Our center cross-sectional study systematically established, for the first time, age-related reference ranges for normal urethral length in pediatric populations (from infant to adolescents), filling a gap in the standardization of developmental anatomy. The application of these reference values in hypospadias repair surgery demonstrated that individualized urethral reconstruction catheterization based on age groups partly reduced postoperative complication rates (e.g., hematuria, pain, overflow).These findings confirm that age-specific urethral length standards hold clear clinical significance for optimizing preoperative planning and postoperative care in congenital anomaly repairs.