Analysis of risk factors for postoperative febrile urinary tract infection in children with primary vesicoureteral reflux

Objective: This study aims to identify risk factors for febrile urinary tract infection (fUTI) after surgery for primary vesicoureteral reflux (VUR) in children. Methods: We conducted a retrospective cohort study of children diagnosed with VUR by voiding cystourethrography (VCUG) who underwent surgical intervention at our institution between January 2019 and December 2024. Patients were grouped based on the occurrence of postoperative fUTI. Univariate analyses were performed, and variables with P < 0.10 were entered into a modified Poisson regression model to identify independent risk factors, with particular focus on the vesicoureteral reflux index (VURx) and distal ureteral diameter ratio (UDR). A modified Poisson regression model with robust variance estimators was used to directly estimate relative risks (RR) due to the non-rare outcome. Results: A total of 79 children (49 girls, 30 boys) were included, with a median surgical age of 28 months. Preoperatively, bladder bowel dysfunction (BBD) was present in 32 patients (40.5%) and renal scarring in 41 (51.9%). During the follow-up period from after stent removal to six months postoperatively, 13 children (16.5%) experienced at least one fUTI. Univariate analysis identified significant associations between postoperative fUTI and higher VUR grade (P = 0.030), higher VURx score (P = 0.001), larger ureteral diameter (P < 0.001), higher UDR (P < 0.001), presence of renal scarring (P = 0.010), and presence of BBD (P = 0.044). Modified Poisson regression analysis revealed that pre-existing renal scarring (RR=1.279, 95% CI 1.093–1.842, P = 0.024), a higher VURx score (RR=3.713, 95% CI 1.328–10.379, P = 0.012), and an increased UDR (RR=199.757, 95% CI 10.943–3646.268, P < 0.001) were independently associated with postoperative fUTI. The area under the curve (AUC) was 0.888 for UDR, 0.773 for VURx, and 0.937 for their combined model. Conclusion: This exploratory analysis suggests that a UDR >0.446, VURx ≥5, and pre-existing renal scarring are associated with an increased risk of fUTI following VUR surgery. These hypothesis-generating findings highlight potential imaging markers for risk stratification but require validation in larger prospective studies.