Role of puboperinealis and rectourethralis muscles as a urethral support system to maintain urinary continence after robot-assisted radical prostatectomy.

The present study investigated the role of a urethral support system to maintain urinary continence after robot-assisted radical prostatectomy (RARP), with a focus on pelvic floor muscles, such as the puboperinealis muscle (PPM) and rectourethralis muscle (RUM). Finally, 323 patients who underwent RARP were analyzed in this study. All patients performed a one-hour pad test 1, 3, 6, 9, and 12 months after RARP to assess urinary incontinence and MRI before and 9 months after RARP to evaluate the pelvic anatomical structure. The preoperative cross-sectional area of PPM (2.21 ± 0.69 cm2) was significantly reduced by 19% after RARP (1.79 ± 0.60 cm2; p < 0.01). Positive correlations were observed between the amount of urinary leakage according to the 1-h pad test 1, 3, 6, 9, and 12 months after RARP and the change in the cross-sectional area of PPM by RARP (p < 0.01, < 0.001, < 0.001, < 0.001, and < 0.001, respectively). A positive correlation was also noted between the amount of urinary leakage 6 and 12 months after RARP and the preoperative RUM diameter (p < 0.05). The amount of urinary leakage 1, 3, 6, 9, and 12 months after RARP negatively correlated with the change in the antero-posterior diameter of the membranous urethra (MU diameter) from the static to dynamic phases during the Valsalva maneuver by cine MRI. Furthermore, the change in the MU diameter negatively correlated with the change in the cross-sectional area of PPM (p < 0.05). PPM and RUM play significant roles as a supportive mechanism to maintain urinary continence by functioning as a urethral support.