The effects of bladder over distention on voiding function in kindergarteners

We report the effects of bladder over distention on pediatric voiding function.

We enrolled healthy kindergarten children (mean age 4.5 +/- 1.0 years) for 2 observations of uroflowmetry and post-void residual urine. Additional observations were requested if the voided volume was less than 50% of expected bladder capacity. Post-void residual was assessed within 5 minutes after voiding. A post-void residual of more than 20 ml is regarded as increased. Bladder capacity is defined as voided volume plus post-void residual and shown as percentage of expected bladder capacity. The uroflowmetry curves were categorized as bell-shaped or nonbell-shaped.

Among 188 children 355 observations of uroflowmetry and post-void residual were eligible for evaluation. Nonbell-shaped uroflowmetry curves and increased post-void residual were noted in 75 (21.1%) and 78 (22%) of 355 voids, respectively. Based on the receiver operating characteristic curve for the nonbell-shaped curves and increased post-void residual, bladder capacity of 115% of expected bladder capacity or more is defined as bladder over distention. There were statistically more increased post-void residuals and more nonbell-shaped uroflowmetry curves in the voids with bladder over distention than in those without over distention (p <0.01). Of the 38 children displaying both types of curves the nonbell-shaped curves usually occurred at a higher bladder capacity than did the bell-shaped curves (133% +/- 46% expected bladder capacity vs 84% +/- 38% expected bladder capacity, p <0.01). Peak uroflow rate increased as bladder capacity increased but decreased at extreme bladder over distention.

Optimal bladder capacity is important for assessing pediatric voiding function. Bladder over distention resulted in more nonbell-shaped uroflowmetry curves and more increased post-void residual. At extreme over distention peak flow rate decreased as well.