Comparison of the puborectal muscle on MRI in women with POP and levator ani defects with those with normal support and no defect

Abstract

Introduction and hypothesis: The objective of this study was to compare puborectal muscle integrity and bulk in women with both major levator ani (LA) defects on MRI and pelvic organ prolapse (POP) to women with normal LA muscle and normal support.

Methods: This is a case-control study comparing 24 cases with known major LA defects and POP to 24 controls with normal LA and normal support. Axial T-2 weighted MRI scans of the pelvis were evaluated for integrity of the puborectal muscle and degree of muscle bulk.

Results: There were no significant group differences in age, body mass index, vaginal deliveries, or hysterectomy status. In all 48 subjects, the puborectal muscle was visible and had no disruption noted. There was no difference in muscle bulk between groups (control/case, thin 42% vs. 25%, average 42% vs. 38%, thick-17% vs. 38%; P = 0.47).

Conclusions: Defects and loss of muscle bulk in the puborectal muscle are not seen on MRI in women with major LA defects and POP.

Fig. 1

Structural orientation to levator ani subdivisions and visibility of the puborectal muscle in MR images at two different levels (chosen from multiple contiguous sections as we followed the puborectal^TA muscle from its origin at the pubic bone to its decussation behind the rectum); a lateral view of 3-D model with pubic bones, (B bladder, U uterus, R rectum), b levator subdivisions: without bones (PCM pubococcygeus muscle, ICM iliococcygeus muscle, PRM puborectal muscle^TA, EAS external anal sphincter). c Level of the PRM decussation showing the scan plane for d, revealing the MRI at level of the PRM decussation (outlined), e level where the PRM “arms” project towards the pubic bone; f MRI at the level of the PRM “arms” (outlined in red)

Fig. 2

Examples of PRM prominence at the point of decussation behind the anorectal junction

Fig. 3

Puborectal^TA prominence in cases versus control groups