INTRODUCTION AND OBJECTIVE:
The aim of this study was to clarify the mechanism of urinary incontinence after robot-assisted radical prostatectomy (RARP) focusing on changes in the pelvic floor muscles.
A total of 323 patients underwent RARP in our hospital from 2014 to 2019 were included and retrospectively analyzed. All patients were analyzed membranous urethral length (MUL), puborectalis muscle (PRM) and rectourethral muscle (RUM) by preoperative and postoperative MRI, and underwent a one-hour pad test 1, 3, 6, 9, 12 months after surgery. The maximum urethral closure pressure (MUCP) was also measured before and after surgery by measuring urethral pressure (UPP). The correlation between postprostatectomy incontinence (PPI) and various factors analyzed by regression analysis.
The PRM cross-sectional area was significantly decreased after surgery (-19%, p<0.001). The urinary incontinence rates at 1, 3, 6, 9 and 12 months after surgery were 40.2%, 63.5%, 73.1%, 74.6% and 76.8%, respectively. A significant correlation between PPI (1,3,6,9,12M) and postoperative MUL (OR:0.10,0.04,0.07,0.04,0.05, p-value: <0.001, <0.001, <0.001, <0.001, <0.001, respectively), or PRM cross-sectional area change after RARP (OR: 2.27, 3.19, 4.60, 2.39, 4.25, p-value: <0.01, <0.001, <0.001, <0.01, <0.001, respectively) was observed. A significant correlation was also observed between post-operative PRM cross sectional area and postoperative MUCP (R=0.510, p<0.001).
The levator ani muscle is thought to be directly or indirectly connected to the RUM. It is speculated that the levator ani muscle and the RUM work like a sling and affect urinary continence. Postoperative reduction of PRM cross-sectional area caused a decrease in the function of the support mechanism as a urethral sling, which affected MUCP and PPI. It was considered important to perform surgery with an awareness of reducing damage to PRM. Furthermore, PPI can be improved by novel techniques to make new support mechanism as a urethral sling using the levator ani muscle.
Source of Funding: