Lowest Acceptable Bladder Capacity for Interpretation of Uroflowmetry Tests in Children

To determine the age-specific lowest acceptable value of bladder capacity (LABC) for interpretation of uroflowmetry tests in children.

From September 2008 through July 2012, healthy children aged 4-9 years were enrolled. All children were asked to have two sets of uroflowmetry and post-void residual (PVR) tests. We selected the tests with lower bladder capacity (voided volume+ PVR) of each child to analyze the LABC. Only bell shaped curves were regarded as normal. PVR >20 mL and Qmax <15 mL/s in children aged 4-6 years, and PVR >10 mL, Qmax <15.0 mL/s in children aged 7-9 years were defined as abnormal, respectively. Receiver operative characteristic curves were used to determine the age-specific cut-off value of LABC. The upper boundary of optimal bladder capacity (OBC) for interpretation of uroflowmetry was defined at 115% expected bladder capacity, and LABC as lower boundary. Linear regression was used to establish the relationship between age and LABC.

Totally, 930 children were eligible for analysis of LABC. Through ROC curve analysis and regression analysis, the best fitted age specific LABC defined though differentiating low Qmax is 52.08 mL + age in years × 4.78 mL. For simplicity, the proposed LABC is age in years × 5 + 50. Good reproducibility of normal flow pattern, Qmax and PVR in each child were observed in the uroflowmetry tests within OBC.

Through the large scale study for uroflowmetry tests in children, we proposed the age-specific lowest acceptable bladder capacity for interpretation of uroflowmetry tests as age in years × 5 + 50 mL.