Urinary bladder volume and pressure at reflux as prognostic factors of vesicoureteral reflux outcome

Background: Controversy exists as to whether the outcome of vesicoureteral reflux (VUR) can be prognosticated by direct radionuclide cystography (DRC).Objective:To correlate the quantitative data obtained by DRC with disease outcome in infants with VUR and positive DRC 1 year after diagnosis. Materials and methods: The medical records of 109 children with known primary VUR diagnosed during the first year of life were studied retrospectively. One year after diagnosis all patients underwent DRC. Children with a positive first DRC were followed up for the next 36 months. Fisher’s exact test was used to calculate the statistical significance of differences in the number of ureters with resolved reflux, as related to quantitative data obtained during the first DRC. Results:The first DRC, performed 1 year after the initial diagnosis, was positive in 49 children (26 with bilateral reflux). Quantitative data derived from this first examination could not establish any prognostic value for a refluxing volume of <2% of the total vesical volume or a reflux at a bladder volume of more than 60% of total bladder capacity. When this limit was lowered to 45%, a statistically significant difference was found (P=0.046). Moreover, when a bladder pressure at the time of reflux of more than 20 cm H₂O was set as a criterion, an extremely significant probability value was calculated (P=0.0009). Conclusions: VUR occurring at a bladder pressure of less than 20 cm H₂O and a filling volume of less than 45% of the total bladder volume indicate a low probability for VUR resolution within the subsequent 36 months, in infants with known reflux.