Bladder neck size and its association with urinary continence after robot-assisted radical prostatectomy

Objectives: This study aims to determine whether bladder neck size (BNS) measured during surgery is associated with urinary continence after robot-assisted radical prostatectomy.Patients and Methods: Between June 2015 and March 2019, 365 consecutive eligible patients undergoing robot-assisted radical prostatectomy were enrolled into a prospective observational cohort study. The primary outcome was patient-reported urinary continence status at 1, 3, 6, 12 and 24 months postoperatively, with continence defined as 0 pad/day. The primary exposure was BNS (largest diameter) measured intraoperatively just before performance of vesicourethral anastomosis. Other covariates included age, body mass index, NCCN risk category, nerve-sparing, membranous urethral length measured intraoperatively and weight of the resected specimen.Results: Well-preserved neurovascular bundle (bilateral/unilateral/none) was highly correlated with urinary continence status at every point after surgery. No difference could be seen between the group with BNS <= 17 mm and the >17-mm group at 1, 3 and 6 months after surgery, but there was better urinary rate of continence in narrow BNS group (<= 17 mm) at 12 and 24 months after surgery. Multivariate analysis showed both nerve sparing and bladder neck diameter to be independent factors affecting urinary continence at 12 and 24 months after surgery.Conclusion: Preservation of neurovascular bundles was associated with better urinary continence after surgery. Smaller BNS was associated with better urinary continence in late stages after surgery (12-24 months after surgery).