Purpose: To estimate functional bladder capacity (FBC) during direct radionuclide cystography and to assess the relationship between vesicoureteral reflux and FBC.
Materials and methods: By using 5,165 direct radionuclide cystograms in patients aged newborn to 14 years, linear and nonlinear models were fit to estimate FBC from age. Analysis was performed on girls and boys separately. In a subgroup, height and weight were evaluated as predictors of FBC. Linear models were used to assess differences in predicted FBC according to sex and reflux status.
Results: The relationship between FBC and age is best described by a nonlinear power function. Percentiles derived from this model are close to the empiric percentiles of FBC. When controlling for age, girls and patients with reflux had larger bladder capacities (P < .01). Height and weight did not improve FBC prediction accuracy.
Conclusion: FBC follows a curve with increasing age. The nonlinear relationship between FBC and age appears to be consistent with maturation in infants and children.