Urodynamic prognostic factors for large post-void residual urine volume after intravesical injection of onabotulinumtoxinA for overactive bladder

The aim of this study was to identify factors predicting large post-void residual (PVR) (defined as ≥200 mL), an important unsolved problem, after an intravesical injection of onabotulinumtoxinA in patients with overactive bladder syndrome. The data showed that 133 of 290 patients had a large PVR after treatment. Multivariate analysis found that the baseline 3-day daytime frequency episodes and voiding efficiency were independent predictors for postoperative large PVR. A receiver operating characteristic (ROC) curve analysis showed the following optimum cut-off values: (1) 3-day daytime frequency episodes = 25, which has a ROC area of 0.72; and (2) voiding efficiency = 89%, which has a ROC area being 0.66. The predicted logit transformation of probability of large PVR, logit(p), for a given 3-day daytime frequency episodes (a) and voiding efficiency (b%) can be denoted by logit(p) = -5.18 + 0.07 × a + 0.04 × b, with a cutoff value of logit(p) = 0.34 and a ROC area of 0.79. The median value of the persistent large PVR interval was 5 months. In conclusion, low 3-day daytime frequency episodes (<25) and low voiding efficiency (<89%) are associated with large PVR. Besides, logit(p) <0.34 can be used to predict large PVR for its higher ROC area.