O3335: Hydroureter as a Key Risk Factor for Urinary Tract Infections in Pediatric Hydronephrosis: Insights from a Large-Scale Analysis

Background: Pediatric hydronephrosis is a common imaging finding that can be indicative of obstruction, thought to predispose infants to an increased risk of urinary tract infection (UTI). Current recommendations for patient selection for antibiotic prophylaxis is mixed. Here, we performed a large risk analysis to assess the effect of concurrent hydroureter, which we hypothesize is the most significant risk factor.

Methods: After research ethics board approval, we retrospectively reviewed our institutional database between Jan 2015 – Dec 2024 to analyze patients with prenatal HN. Patients with prenatal hydronephrosis or hydroureteronephrosis were included. We excluded those with other congenital anomalies (e.g. vesicoureteral reflux, lower tract obstruction, ectopic ureter), late diagnoses (>1 year), short follow-up ( < 6 months), or prior pyeloplasty. The primary outcome was time-to-UTI. We assessed risk factors included sex/circumcision status, and initial ultrasound findings. Hydroureter was considered APD > 6 mm, and high-grade hydronephrosis was considered Society for Fetal Urology (SFU) grade 3/4. Continuous antibiotic prophylaxis (CAP) was defined as longer than 6 months, and generally stopped by one year of age. Kaplan-Meier curves and Cox regression were used to assess for association.

Results: In total, 841 patients (82% male) with median follow-up of 26 months (IQR 14, 43). On initial ultrasound, 137 (16%) patients had hydroureter > 6 mm, 258 (31%) had SFU grade 4 hydronephrosis, and 240 (29%) had APD > 15 mm. 78 patients (9%) developed a UTI. Within the UTI group, the median age of UTI was 8 months (IQR 5, 16). Patients who had developed UTI were more likely to have history of non-refluxing megaureter (47% vs. 18%, p< 0.001), demonstrate hydroureter on ultrasound (42% vs. 13%, p< 0.001), and prolonged CAP (50% vs. 27%, p< 0.001), than the UTI-free group. On survival analysis, high-grade hydronephrosis (HR 1.9, 95%CI 1.2, 3.0; p=0.001), and hydroureter (HR 3.8, 95%CI 2.1, 6.9; p< 0.001) were associated with an increased likelihood of UTI. On multivariable Cox regression, hydroureter and prolonged CAP exposure were significant predictors (Table 1), while high-grade hydronephrosis was not. A Cox regression model performed with a c-index of 0.71 in predicting risk for UTI within this population.

Conclusion: This large-scale analysis highlights the significant role of concurrent hydroureter as a key risk factor for UTIs in infants with pediatric hydronephrosis. Our findings suggest that hydroureter, rather than high-grade hydronephrosis alone, is strongly associated with UTI development. Additionally, prolonged use of CAP appears to be linked with an increased risk of UTI, raising important questions about its long-term efficacy and potential drawbacks. These results emphasize the need for a more tailored approach in selecting candidates for CAP.