Predicting Breakthrough Urinary Tract Infection: Comparative Analysis of Vesicoureteral Reflux Index, Grade and Ureteral Diameter Ratio.

PURPOSE: Vesicoureteral Reflux Index (VURx) is a simple, validated tool for prediction of vesicoureteral reflux (VUR) resolution. Along with likelihood of spontaneous resolution, identification of children at risk for febrile urinary tract infection (fUTI) impacts management. We evaluated the utility of VURx as a predictive factor for breakthrough fUTI compared to VUR grade and distal ureteral diameter ratio (UDR). MATERIALS AND METHODS: Children with primary VUR and detailed voiding cystourethrogram (VCUG) data were identified. A 1-6 point VURx was assigned and UDR computed by measuring largest ureteral diameter within the pelvis and dividing by the distance between L1-L3 vertebral bodies. Random forest modeling and logistic multivariable regression were employed to estimate the predictability of grade, UDR and VURx with regard to breakthrough fUTI. RESULTS: One hundred and thirty-nine children (94 girls, 45 boys) were analyzed with a mean age at diagnosis of 5.4 +/- 4.7 months. Mean length of follow-up was 32.1 +/- 24.5 months. Thirteen children (9.4%) experienced breakthrough fUTI. On univariate analysis, UDR (p = 0.01) and VURx (p = 0.0005) were associated with breakthrough UTI, while grade (p = 0.09) did not reach significance. Area under the curve was generated as a measure of accuracy for each variable and was 0.77 for VURx, 0.71 for UDR and 0.68 for grade, demonstrating superiority of VURx for predicting breakthrough fUTI. CONCLUSIONS: Children with higher VURx are at increased risk for breakthrough febrile UTI independent of reflux grade. VURx provides valuable prognostic information about infection risk facilitating improved clinical decision-making.