Lowest Acceptable Bladder Capacity for Interpretation of Uroflowmetry Tests in Children.

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

METHODS: 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.

RESULTS: 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.

CONCLUSION: 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.