Is exceeding estimated bladder capacity during voiding cystourethrograms harmful?

The purpose of this study was to compare the actual bladder capacity of children undergoing voiding cystourethrogram (VCUG) with existing formula-derived estimates and to describe any adverse effects of bladder overdistention during VCUG.

This retrospective study involved review of 884 consecutive VCUG performed over 3 years. Cases with underlying conditions that could artificially increase bladder capacity, such as neurogenic bladders or vesicoureteral reflux, were excluded.

Included were 440 normal VCUG procedures. Bladder volumes exceeded the expected bladder capacity set by the American Academy of Pediatrics (AAP) and American College of Radiology in 284 VCUG (65%). Of 261 VCUG performed on children <2 years of age, 164 (63%) VCUG exceeded the expected capacity. In the 2- to 14-year-old age group, 113 (68%) of the 165 VCUG performed exceeded the expected bladder capacity. Among the 14 VCUG performed on children >14 years of age, 7 (50%) exceeded the bladder capacity. No adverse effects were found after the VCUG in the 32 VCUG (7.3%) requiring a contrast volume of more than 2 times the AAP estimates and in the 22 VCUG studies (5%) requiring a contrast volume of more than 3 times the AAP estimates.

This study suggests that current guidelines often underestimate bladder capacity, and exceeding the expected bladder capacity appears to be reasonably safe without the occurrence of complications.

Current AAP guidelines often underestimate the capacity of the urinary bladder. Exceeding the expected bladder capacity appears to be reasonably safe.