Vaginal high-pressure zone assessed by dynamic 3-dimensional ultrasound images of the pelvic floor

Abstract

The purpose of this study was to determine the shape and characteristics of the vaginal high-pressure zone (HPZ) by imaging a compliant fluid-filled bag that had been placed in the vaginal HPZ with the 3-dimensional ultrasound system. Nine nulliparous asymptomatic women underwent 3-dimensional ultrasound imaging and vaginal pressure measurements. A compliant bag was placed in the vagina and filled with various volumes of water. Three-dimensional ultrasound volumes of the pelvic floor were obtained at each bag volume while the subjects were at rest and during pelvic floor contraction. At low volumes, the bag was collapsed for a longitudinal extent of approximately 3.3 +/- 0.2 cm (length of vaginal HPZ). With increasing bag volume, there was opening of the vaginal HPZ in the lateral dimension before the anteroposterior dimension. Pelvic floor contraction produced a decrease in the anteroposterior dimension but not the lateral dimension of the bag in the region of the vaginal HPZ. We propose that the shape and characteristics of the vaginal HPZ are consistent with the hypothesis that the puborectalis muscle is responsible for the genesis of the vaginal HPZ.