The sensitivity of pressure specific bladder volume versus total bladder capacity as a measure of bladder storage dysfunction.

Assessment of bladder storage function requires an accurate measure of bladder capacity and pressure. Pressure specific bladder volume is the volume that a bladder can accommodate at a specific pressure. A total of 21 consecutive children with neurogenic bladders who were candidates for bladder augmentation based on standard clinical criteria (upper urinary tract deterioration, incontinence and infection) was studied to determine the efficacy of pressure specific bladder volume as a measure of bladder dysfunction. Urodynamic indexes were compared to previously established nomograms. All 21 patients had bladder volumes at pressures of 30 cm. water or less, which decreased below the 5th percentile as determined by the nomogram. In 7 patients (33%) normal total bladder capacity was achieved at the expense of elevated storage pressures. Pressure specific bladder volume provides a better measure of bladder storage function than total bladder capacity because it relates volume to intravesical pressure, does not rely on a subjective end point to bladder filling, and is objective and reproducible.