Postpartum Perineal Complex Disruption in 3D Endovaginal Ultrasound

Objectives: Hiatal enlargement is an important precursor to prolapse development and a cause of operative failure. Levator defects are only present in 40% of prolapse patients and explain 15% of hiatus size variation. To better understand how other Level III structures might be disrupted by childbirth, we assessed postpartum structural changes to the perineal complex using 3D endovaginal ultrasound.

Methods: Secondary analysis of 126 primipara at 6 months postpartum who underwent 3D endovaginal ultrasound for a pelvic floor recovery study. Subjects were divided into three groups: 1) Spontaneous vaginal delivery without levator defect (LAD) (n=70); 2) Spontaneous vaginal delivery with levator defect (n=24); and 3) Cesarean section without second stage of labor (n=32). Scans were obtained using a 3D endovaginal ultrasound machine and imported into 3D Slicer (www.slicer.org/). The following anatomic landmarks were used to ensure the region of interest (perineal complex) was being analyzed: superficial transverse perineal muscle, levator ani, posterior vaginal wall, and anal sphincter. While reviewing scans blinded to delivery mode, two imaging patterns that suggested injury were discovered: a) Loss of the normal band of tissue connecting the two sides of the perineal complex between vagina and rectum; b) Loss of the “pinched waist” configuration of tissues, which usually appears as a triangular indentation on each side (Figure 1). Loss of these patterns seemed to reflect disruption of tissue convergence across the midline. Each pattern was classified as being present (score 0), equivocal (score 1) or absent (score 2). Each subject then received a total score from 0 to 4 by summing the two individual scores.

Results: Subjects had mean age of 30.7±4.6 years and mean BMI of 31.9±6.2kg/m2. In the vaginal delivery without LAD group, 29% showed disruption of the band of tissue, 26% showed loss of the pinched waist sign, and 39% had a total score of 3 or 4 (one or both features absent). In the c-section group, about 10% showed disruption of each reported pattern, and 85% had lower total scores (0, 1 or 2) which was 2.5x the rate of low scores in women with LAD. Women with LAD showed the greatest occurrence of disruption with a 58% absence of band of tissue and 42% loss of pinched waist sign (Figure 2).

Conclusions: Novel childbirth-related structural changes in the perineal complex can be documented with 3D endovaginal ultrasound. Comment: If these disruptions are proven to be associated with hiatal enlargement, they are potentially repairable and preventive interventions could be developed.
Figure 1. Axial ultrasound scan examples of present (a), equivocal (b), and absent (c) band of tissue (between arrowheads) and pinched waist sign (dotted line).
Figure 2. Percentage of subjects by delivery group for band of tissue (a), pinched waist sign(b), total score (c).