In vivo assessment of the elastic properties of the external anal sphincter in term pregnant women using shear wave elastography

Introduction and hypothesis The objective was to assess the intraobserver intersession and interobserver intrasession reliability of shear wave elastography applied to the external anal sphincter in term pregnant women. Methods This prospective study involved nulliparous pregnant women at 37 weeks or more with two visits (V1: one observer; V2 two observers) planned within a 12-h to 7-day interval. Measurements were performed using an Aixplorer V12® device with an SL 18-5 linear probe using a transperineal approach, allowing a measurement of the shear modulus (SM) in kPa. Measures were performed at rest, Valsalva maneuver, and maximal contraction. Reliability was assessed using the intraclass correlation coefficient (ICC). The study was approved by an ethics committee (ID RCB: 2020-A00764-65). Results A total of 37 women were included. Intraobserver reliability was excellent at rest (ICC = 0.91 [0.84–0.95) and good during the Valsalva maneuver (ICC = 0.83 [0.72–0.90]) and contraction (ICC = 0.85 [0.75–0.91]). Interobserver reliability was good at rest (ICC = 0.79 [0.66–0.87]) and during Valsalva (ICC = 0.84 [0.73–0.90]), but moderate during contraction (ICC = 0.70 [0.53–0.82]). Conclusions Shear wave elastography is a reliable tool for assessing the elastic properties of the external anal sphincter in term pregnant women.