Female striated urogenital sphincter contraction measured by shear wave elastography during pelvic floor muscle activation: Proof of concept and validation.

Abstract

Investigation of the function of the striated urogenital sphincter (SUS) is challenging because it is difficult to access and requires invasive measures. Ultrasound shear wave elastography (SWE) is a non-invasive real-time technique used to estimate tissue stiffness. As muscle stiffness can be used as an estimate of muscle force, SWE provides an opportunity to study contraction of the peri-urethral musculature. Validation of SWE to study SUS during functional tasks, such as pelvic floor muscle contractions, is required prior to application in clinical populations. Ten healthy females (34[5] years) participated. Stiffness in a region expected to contain the SUS was quantified using SWE at rest and during a pelvic floor muscle contractions performed at 10%, 25%, and 50% of maximal voluntary contraction (MVC). Two repetitions were performed for 10 s. During contraction, stiffness increased in the region of the SUS in all participants and at all contraction intensities. Multiple regions of increased stiffness were detected, with 95.8% of regions situated ventral to the mid-urethra within the anatomical area of the SUS. The increase in stiffness was greater for 50% MVC than both 10% and 25% MVC contraction intensities (P < 0.01). Stiffness increased within the anatomical region of the SUS during voluntary pelvic floor muscle contractions with predictable response to changes in contraction intensity. These observations support the potential for ultrasound SWE to study SUS function non-invasively.