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

Abstract

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.Methods: 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. Results: 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 postprostatectomy 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.Conclusions: 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.

Contribution of Retzius-sparing robot-assisted radical prostatectomy to the mechanism of urinary continence as demonstrated by dynamic MRI

“…The PB-AR during abdominal pressure is thought to move in the direction of shortening (positive distribution) and UVJ movement in the cephalic direction (zero to negative distribution) when PFMT are effective in urinary continence, and these movements are reportedly effective in urinary continence 8 , 9 , 11 . Several RCTs have been conducted on the effect of PFMT on reducing urinary incontinence after RP.…”

“…Recently, many anatomical studies that use magnetic resonance imaging (MRI) have reported that membranous urethral length (MUL) affects postoperative urinary continence, which may be related to resting urethral closure pressure 3 – 7 . The mechanism of SUI has also been investigated using transperineal ultrasound and dynamic MRI, and several studies reported on the relationship between pelvic anatomy changes during abdominal pressure and postoperative urinary incontinence 8 – 11 . Additionally, many surgical techniques have been reported to reduce postoperative urinary incontinence.…”

Impact of Pelvic Anatomical Changes Caused by Radical Prostatectomy

“…The mechanism of urethral closure during abdominal pressure has been observed in the pre-RP state, as well as in studies using transperineal ultrasound and dynamic MRI. The anterior wall of the rectum is reported to move in the direction of the pubic bone simultaneously with the applied abdominal pressure, and it is thought that this is observed mainly because the urethra is compressed in the anterior-posterior direction by the action of the levator ani muscle, resulting in increased pressure at urethral closure [61,62]. In a report examining pelvic anatomical changes during abdominal pressure after RP, the anterior wall of the rectum moved less toward the pubic bone than before RP, which is thought to affect the urethral sphincter closure pressure, resulting in an increased probability of stress urinary incontinence [62,63].…”

“…The anterior wall of the rectum is reported to move in the direction of the pubic bone simultaneously with the applied abdominal pressure, and it is thought that this is observed mainly because the urethra is compressed in the anterior-posterior direction by the action of the levator ani muscle, resulting in increased pressure at urethral closure [61,62]. In a report examining pelvic anatomical changes during abdominal pressure after RP, the anterior wall of the rectum moved less toward the pubic bone than before RP, which is thought to affect the urethral sphincter closure pressure, resulting in an increased probability of stress urinary incontinence [62,63]. In fact, the abdominal leak point pressure test shows that urine leakage during abdominal pressure, which was rarely observed preoperatively, is observed in an increasing number of cases after RP, indicating that a decrease in urethral closure pressure during abdominal pressure occurs after RP [58,60].…”

“…In fact, the abdominal leak point pressure test shows that urine leakage during abdominal pressure, which was rarely observed preoperatively, is observed in an increasing number of cases after RP, indicating that a decrease in urethral closure pressure during abdominal pressure occurs after RP [58,60]. MRI and transperineal ultrasound observations during abdominal pressure application have shown that the closure mechanism during abdominal pressure application does not work well in cases with high urinary incontinence after RP [62,64].…”