Reference ranges for cystographic bladder capacity in children-with special attention to vesicoureteral reflux

Linear correlations for cystometric/cystographic bladder capacity with age universally serve as clinical yardsticks in pediatric urology and nephrology. However, these correlations do not account for growth or the range in values, as the relation of cystometric/cystographic bladder capacity with age is nonlinear. Also, vesicoureteral reflux might influence the size of cystometric/cystographic bladder capacity, since small and large bladder capacities have been reported in conjunction with reflux. We decided to use the data sets of the International Reflux Study in Children to construct full reference ranges for cystometric/cystographic bladder capacity and age, for comparison with existing reference ranges in normal children, and to study the relation between bladder capacity and refluxing volume.

In the International Reflux Study in Children 386 patients with grade III or IV vesicoureteral reflux were followed with isotope cystography for 10 years. To follow the grade of reflux, x-ray cystography was also used at 60-month intervals. The 386 children, who were 1 month to 12 years old, were randomized into 2 groups-those undergoing surgery and those receiving medical treatment. For both groups data were available on cystometric/cystographic bladder capacity, refluxing volume, reflux grade and reflux outcome.

The distribution of cystometric/cystographic bladder capacity vs age is logarithmic, with a wide range between the 5th and 95th percentiles, and a clear nonlinear relation between bladder capacity and age (p < 0.001). Gender has no influence on cystometric/cystographic bladder capacity. No difference in bladder capacity exists between persistence or resolution of vesicoureteral reflux (p < 0.78), between grade III and grade IV reflux (p < 0.94), or between unilateral and bilateral reflux (p < 0.74). Thus, refluxing volume correlated only with reflux grade, not with cystometric/cystographic bladder capacity or age.

With or without vesicoureteral reflux values for cystometric/cystographic bladder capacity range widely in children, and correlate logarithmically with age. For clinical decisions the full reference range for age, flanked by the 5th and 95th percentiles, should be used to assess individual values for cystometric/cystographic bladder capacity, rather than linear functions.