Background and Objective: Urinary tract infection (UTI) is a common pediatric infection. Vesicoureteral reflux (VUR) is a significant risk factor for associated renal complications. The optimal timing for voiding cystourethrography (VCUG), the diagnostic gold standard, remains controversial. This study compared the prevalence of VUR detected by VCUG performed after the first versus the second UTI in young children.

Materials and Methods: In this cross-sectional study, 305 children aged 3-24 months with UTI were enrolled at Hazrat-e Masoumeh Hospital, Qom. Participants were divided into two groups: those undergoing VCUG after their first UTI (n=208) and after their second UTI (n=97). Demographic, ultrasound, and VCUG data were collected. Statistical analysis included Chi-square, t-tests, and logistic regression.

Results: The overall VUR prevalence was 20.3% (62/305). The frequency was significantly higher in the second-UTI group (30.9%) compared to the first-UTI group (15.4%). Logistic regression identified a second UTI episode as an independent risk factor for VUR (Adjusted OR=0.411, p=0.003), equating to 2.43 times higher odds. No significant association was found between VUR and patient age (p=0.325) or sex (p=0.677). The mean age was 11.93±4.67 months, with a female-to-male ratio of 54.1% to 45.9%.

Conclusion: A second UTI episode is an independent predictor of VUR in children aged 2-24 months, underscoring the importance of targeted VCUG screening after recurrent infection to enable timely intervention. Age and sex were not significant risk predictors in this cohort.

Keywords: Vesicoureteral Reflux, Urinary Tract Infection, Voiding Cystourethrography, Child, Recurrence.