Posterior vaginal prolapse shape and position changes at maximal Valsalva seen in 3-D MRI-based models

Two-dimensional magnetic resonance imaging (MRI) of posterior vaginal prolapse has been studied. However, the three-dimensional (3-D) mechanisms causing such prolapse remain poorly understood. This discovery project was undertaken to identify the different 3-D characteristics of models of rectocele-type posterior vaginal prolapse (PVP(R)) in women.

Ten women with (cases) and ten without (controls) PVP(R) were selected from an ongoing case-control study. Supine, multiplanar MR imaging was performed at rest and maximal Valsalva. Three-dimensional reconstructions of the posterior vaginal wall and pelvic bones were created using 3D Slicer v. 3.4.1. In each slice the posterior vaginal wall and perineal skin were outlined to the anterior margin of the external anal sphincter to include the area of the perineal body. Women with predominant enteroceles or anterior vaginal prolapse were excluded.

The case and control groups had similar demographics. In women with PVP(R) two characteristics were consistently visible (10/10): (1) the posterior vaginal wall displayed a folding phenomenon similar to a person beginning to kneel ("kneeling" shape) and (2) a downward displacement in the upper two thirds of the vagina. Also seen in some, but not all of the scans were: (3) forward protrusion of the distal vagina (6/10), (4) perineal descent (5/10), and (5) distal widening in the lower third of the vagina (3/10).

Increased folding (kneeling) of the vagina and an overall downward displacement are consistently present in rectocele. Forward protrusion, perineal descent, and distal widening are sometimes seen as well.