WITHDRAWN: The lowest acceptable bladder capacity for interpretation of uroflowmetry tests in children

Abstract

Summary Introduction Under- or overdistended bladder is associated with impaired bladder emptying. Therefore, uroflowmerty of low bladder capacity is regarded as irrelevant for interpretation. However, is no general consensus with regard to the lowest acceptable value of bladder capacity (LABC) for interpretation of uroflowmetry in children. Objective The objective was to determine the age-specific lowest acceptable value of bladder capacity in children. Study design From September 2008 to July 2012, healthy children aged 4–9 years were enrolled for analysis. An uroflowmeter was placed in the toilets at each kindergarten or elementary school. All post-void residual urine (PVRs) was assessed within 5 minutes after voiding by suprapubic ultrasound, and estimated by the equation of height × width × depth × 0.52 mL. All children were asked to have two sets of uroflowmetry and PVR tests. Two pediatric urologists reviewed the uroflow patterns and classified the uroflow patterns as bell-shaped, intermittent, tower, plateau, and staccato-shaped. We selected tests of lower bladder capacity (voided volume + PVR) from each child to analyze the optimal cut-off value for defining the LABC. Only bell-shaped curves were regarded as normal. PVR > 20 mL and Q max 10 mL, Q max Q max and high PVR, receiver operative characteristic curves (ROC) were used to determine the age-specific cut-off value of LABC. The upper boundary of optimal bladder capacity for interpretation of uroflowmetry was defined at 115% expected bladder capacity (EBC, age in years × 30 + 30 mL), and LABC as the lower boundary. Linear regression was used to establish the relationship between age and LABC. Results In total, 930 children were eligible for analysis of LABC. Through ROC curve analysis and regression analysis, the best-fitted age-specific LABC defined by differentiating low Q max (A) and high PVR (B) is 52.08 mL + age in years × 4.78 and 85.79 mL + age in years × 7.64 mL, respectively. For simplicity, the proposed LABC- Q max (A) and LABC-PVR (B) is age in years × 5 + 50 (LABC- Q max ) and age in year × 7.5 + 85 mL (LABC-PVR), respectively. Better reproducibility of normal flow pattern, Q max and PVR in each child were observed in the uroflowmetry tests both performed below the 115% EBC and above the LABC- Q max . Therefore, we chose LABC- Q max as the preferred lowest acceptable bladder capacity for interpretation of uroflowmetry tests. Discussion The current study used a physiological approach to determine the lowest acceptable values of bladder capacity that urinary bladder can have adequate performance for normal flow pattern, good peak flow rate, and low PVR. Within the optimal bladder capacity (upper boundary as 115% expected bladder capacity and lower boundary as LABC- Q max ), the reproducibility of uroflowmetry tests is good which improved the reliability of uroflowmetry tests. Conclusions 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.