Can we identify the limits of the puborectalis/pubovisceralis muscle on tomographic translabial ultrasound?

Abstract

In order to determine the relative locations of puborectalis/pubovisceralis (PR/PV) and iliococcygeus (IC) muscles, we undertook an analysis of four-dimensional (4D) ultrasound datasets obtained after suburethral sling placement. This was a retrospective analysis of ultrasound volume data obtained in 110 women after undergoing the Monarc suburethral sling procedure. Tomographic ultrasound imaging (TUI) was performed with eight slices in the axial plane, from 5 mm below to 12.5 mm above the plane of minimal hiatal dimensions. Hyperechogenic tape material was rated as absent, present or as producing an anechoic acoustic shadow overlying the muscle in each slice. Slices 7 and 8 virtually always showed evidence of the implant or its acoustic shadow on the pelvic sidewall (98% for slice 8 and 96% for slice 7), suggesting that these slices are located at the level of the obturator foramen. This implies that these slices do not generally contain PR/PV muscle, but rather IC muscle. On standardized tomographic imaging of the levator hiatus and muscle, slices located ≥ 1 cm over the plane of minimal dimensions are very likely to contain IC muscle rather than PR/PV muscle.