The null effect of bladder neck size on incontinence outcomes after radical prostatectomy

Purpose: We sought to determine whether bladder neck size is associated with incontinence scores after robot-assisted laparoscopic radical prostatectomy. Materials and Methods: Consecutive eligible patients undergoing robot-assisted laparoscopic radical prostatectomy between July 19 and December 28, 2016 were enrolled in a prospective, longitudinal, observational cohort study. The primary outcome was patient reported urinary incontinence on the EPIC (Expanded Prostate Cancer Index Composite) scale 6 and 12 weeks postoperatively. The relationship between the EPIC score of urinary incontinence and bladder neck size was evaluated by multiple regression. Predicted EPIC scores for incontinence were displayed graphically after using restricted cubic splines to model bladder neck size. Results: A total of 107 patients were enrolled. The response rate was 98% and 87% at 6 and 12 weeks, respectively. Bladder neck size was not significantly associated with incontinence scores at 6 and 12 weeks. Comparing the 90th percentile for bladder neck size (18 mm) with the 10th percentile (7 mm) revealed no significant difference in adjusted EPIC scores for incontinence at 6 weeks (b coefficient 0.88, 95% CI -10.92-12.68, p = 0.88) or at 12 weeks (b coefficient 5.80, 95% CI -7.36-18.97, p = 0.39). Conclusions: These findings question the merit of creating an extremely small bladder neck during robot-assisted laparoscopic radical prostatectomy. We contend that doing so increases the risk of positive margins at the bladder neck without facilitating early recovery of continence.