Evaluation of the effect of levator ani muscle contraction on post‐prostatectomy urinary incontinence using cine MRI

Post-prostatectomy urinary incontinence (PPI) is the greatest concern for urologists after radical prostatectomy (RP). It is thought that PPI is composed of multiple factors including static and dynamic components. The purpose of this study is to show visually levator ani muscle (LAM) contraction during pelvic floor muscle contraction and to evaluate the dynamic differences in its contraction between men with and without PPI.This study was a case-control study of the urinary continent or incontinent men. It investigated whether LAM contraction was involved in urinary leakage based on examination of LAM contraction by cine magnetic resonance imaging.The LAM contracted from the coccyx to the pubis in the same manner before and after surgery. The degree of contraction of the LAM in post-prostatectomy groups was smaller than that in the healthy adult group. The contraction distances of each part of the pelvic floor were decreased by 50%-70% in the incontinence group compared to those in the continence group. The bladder neck moved 2.5-fold further in the continence group and the direction of movement was more vertical than in the incontinence group. Urethral compression was attenuated by about 40% in the incontinence group compared to that in the continence group.RP can cause damage to the LAM. LAM contraction is reduced after RP compared with that in healthy adult men. In men with PPI, the reduced muscle contraction might not compress the urethra sufficiently when abdominal pressure is raised. Pelvic floor muscle training might provide a meaningful method for the recovery of LAM contraction in patients with PPI.