Quantifying Levator Ani Muscle Elasticity Under Normal and Prolapse Conditions by Shear Wave Elastography: A Preliminary Study.

Objectives The primary purpose of this study was to determine whether elasticity quantification of the levator ani muscle (LAM) using shear wave elastography (SWE) is different between women with and without pelvic organ prolapse (POP) and to determine whether LAM elasticity is associated with the prolapse stage or the dimensions of the levator hiatus. The secondary aim was to evaluate the intraobserver and interobserver reliability of LAM elasticity measurements using SWE. Methods The study participants included 20 women with normal pelvic support and 38 women with prolapse (stages I-III). The levator hiatus was imaged by transperineal 3-dimensional ultrasound, and LAM elasticity and the elastic modulus were measured by SWE at rest and while performing the Valsalva maneuver. Results The elastic modulus increased significantly from rest to during to maximal Valsalva maneuver (29.2 versus 54.1 kPa; P < .05) in all women. Levator ani muscle elasticity was significantly higher under prolapse conditions than under normal conditions at rest (27.9 versus 31 kPa; P < .001) but was lower during the maximal Valsalva maneuver than under normal conditions (57.3 versus 53.1 kPa; P < .05). Levator ani muscle elasticity at rest was associated with the hiatus area during the Valsalva maneuver (Spearman r = 0.608; P < .001) and distensibility of the levator hiatus (r = 0.594; P < .001), and the hiatus area decreased as the LAM elastic modulus increased during the maximal Valsalva maneuver (r = -0.414; P < .05). Moreover, LAM elasticity was associated with the severity of prolapse (P < .001). Conclusions As a noninvasive quantitative method, SWE, may be used to assess the biomechanical properties of the pelvic floor muscle, providing some research basis for a thorough understanding of POP and its treatment and prevention.