Perineal Membrane Structural Changes: An Unstudied Aspect of Prolapse

INTRODUCTION AND HYPOTHESIS: The perineal membrane (PM), perineal body, and levator ani muscles form the perineal complex, which is responsible for hiatal closure. Yet failures in its connective tissues that may lead to hiatal closure impairment are poorly understood. We tested the hypothesis that pelvic organ prolapse involves PM abnormalities by comparing PM morphology between young women with prolapse and parous controls using a validated MRI-based reconstruction and analysis technique. METHODS: . Six PM parameters were measured: swinging door angle, visible bony origin length, hiatal anteroposterior diameter and area, PM surface area, and midline separation. Group comparisons used t tests, with Cohen's d, correlations, and stepwise regression analysis. RESULTS: Resting MRIs from 17 young parous women (aged < 40 years) with prolapse and 20 parous controls were compared. Women with prolapse showed 23% greater midline separation of the PM, 30% larger hiatal area, 26% larger hiatal anteroposterior diameter, 17% longer bony origin, and 26% larger PM surface area (all p ≤ 0.002, d = 1.1-1.6); swinging door angle was similar between groups (p = 0.60). Levator ani status, midline separation, and PM surface area independently predicted prolapse, explaining 76% of variance. CONCLUSIONS: The PM structure was altered in those with prolapse through loss of central PM connection, hiatal elongation, and hiatal widening. Larger studies are needed to confirm and guide targeted repair techniques that could potentially prevent prolapse development and/or progression.