Development of a prediction model for urinary tract infection risk after open reimplantation in children with primary unilateral vesicoureteral reflux: A multicentre study.

Objectives: To develop a predictive model for symptomatic postoperative febrile urinary tract infections (UTIs) in children undergoing open reimplantation for vesicoureteral reflux (VUR) and evaluate the association with VUR recurrence. Patients and methods: This multicentre retrospective study included children with unilateral VUR (grades III-V) who underwent open Cohen or Lich-Gregoir reimplantation (2010-2022), had recurrent febrile UTIs, and ≥1 year follow-up. Analyses used 10-pooled multiple imputation, with complete case for sensitivity. Full and Least Absolute Shrinkage and Selection Operator (LASSO) Weibull regression models with centre clustering, bootstrapping, and 10-fold cross-validation identified predictors. Prediction used demographic, clinical, procedural and antibiotic factors. The non-scaled LASSO model informed the nomogram, evaluated using C-indices, calibration and decision curve analysis (DCA). UTI and VUR recurrence were analysed via cumulative incidence. Results: A total of 404 children (median age 8 (6-9) years; follow-up 2.3 (2.0-3.3) years, 233 complete-case) were analysed. Median preoperative febrile UTIs were four, 74.5% had antibiotic resistance and median postoperative prophylaxis was two days. The 3-year cumulative incidence of postoperative UTI was 27.2% (95% CI: 22.9-31.6). LASSO-significant predictors included operative time (HR 1.10, 95% CI 1.03-1.16); in sensitivity analyses, prior injection (HR 2.08, 95% CI 1.88-2.30) and postoperative antibiotic duration (HR 0.81, 95% CI 0.69-0.97) were also significant. The nomogram included preoperative fever, antibiogram resistance, renal defect, VUR phase, prior injection, surgical indication, catheterization, hospitalization and stenting. The model performed well (C-indices = 0.743; calibration slope = 1), with DCA supporting clinical utility for 10-40% predicted risk. Recurrent VUR grade ≥II after 12 months (3.3%-12.7% at 1-3 years, n = 273) did not increase UTI risk. Conclusions: Children with unilateral dilating VUR remained at risk of postoperative febrile UTIs. The nomogram can assist in identifying high-risk children for targeted interventions, but requires external validation and refinement.