Bladder Volume at Onset of Vesicoureteral Reflux is an Independent Risk Factor for Breakthrough Febrile Urinary Tract Infection

Purpose: Improved identification of children with vesicoureteral reflux at risk for recurrent febrile urinary tract infection may impact management decisions. We hypothesized that reflux occurring earlier during bladder filling increases the duration of exposure of the kidneys to bacteria, and, therefore, increases the risk of pyelonephritis. Materials and Methods: Children with vesicoureteral reflux and detailed voiding cystourethrogram data were identified. Bladder volume at onset of reflux was normalized for age. Demographics, reflux grade, laterality, presence/absence of bladder-bowel dysfunction and breakthrough febrile urinary tract infections were assessed. Median followup was 24 months (IQR 12 to 52). Results: A total of 208 girls and 47 boys were analyzed with a mean +/- SD age at diagnosis of 3.1 +/- 2.6 years. On univariate analysis history of febrile urinary tract infection (HR 2.17, 95% CI 1.33-2.85, p = 0.01), dilating vesicoureteral reflux (HR 1.6, 95% CI 1.05-2.42, p = 0.03) and bladder-bowel dysfunction (HR 1.66, 95% CI 0.99-2.75, p = 0.05) were associated with an increased risk of breakthrough febrile urinary tract infection. Median bladder volume at onset of reflux in children with breakthrough febrile urinary tract infection was significantly less (33.1%) than in those without infection (49.5%, p = 0.003). Reflux onset at 35% predicted bladder capacity or less was associated with a significantly increased risk of breakthrough febrile urinary tract infection on multivariate analysis (HR 1.58, 95% CI 1.05-2.38, p = 0.03). Conclusions: Children with early filling vesicoureteral reflux are at increased risk for breakthrough febrile urinary tract infection independent of reflux grade. Bladder volume at onset of reflux should be recorded during cystograms since it provides additional prognostic information about the risk of pyelonephritis and resolution, and may assist with counseling and clinical decision making.