Endovaginal Ultrasound Study of Puboanal Fibromuscularis and the Posterior Arcus

Perineal instability is a stressful condition for women. The study evaluates the relationship of the puboanal and puboperineal fibromuscularis to the perineal body and the pelvic floor.

The objective of this study was to describe the ultrasound anatomy of the puboanalis (PA) and its relationship to the arcus tendineus rectovaginalis (ATRV) in patients with and without posterior vaginal wall prolapse.

This study included descriptive anatomy of 37 patients with rectocele (points Ap and Bp ≥0) and 22 nulliparous patients without, who completed a questionnaire, pelvic examination, and a 3-D endovaginal ultrasound (EVUS). Posterior compartment structures, PA, and ATRV were traced on EVUS desktop software. PA volume was segmented starting from the superficial transverse perinei and continued 5 mm stepwise to a length of 2.5 cm cephalad. Two independent observers confirmed visualization and volumes.

PA has a butterfly-like structure, encircling the anal canal at one end, traversing anteriorly to insert in the retropubic fascia cephalad, becoming continuous with investing fascia of the pelvis and the lateral rectovaginal fascia attachments at ATRV. Nulliparous patient PA mean volume was 4.45 cm 3 (SD: 0.96), total length of 2-2.5 cm. Ultrasound and cadaveric anatomy are highly correlated. Mean PA volume in the posterior vaginal wall prolapse group was 5.6 cm 3 (22% volume increase compared with nulliparous group); 48% had ATRV defects on the right side, and 54% had PA injuries on the left side. Bilateral ATRV defects were present in 27%, and 75% on at least one side.;33% of nulliparous patients, and 95% of posterior vaginal wall prolapse patients had splinting or bulge symptoms.

PA stabilizes the anal outlet and merges with posterior vaginal support. The disruption of ATRV attachment was common in posterior vaginal wall prolapse.