Anal sphincter imaging: better done at rest or on pelvic floor muscle contraction?

Introduction And Hypothesis: Exo-anal ultrasound imaging of the anal sphincter is usually undertaken on pelvic floor muscle contraction (PFMC) as this seems to enhance tissue discrimination. Some women are unable to achieve a satisfactory PFMC, and in this situation, the sphincter is assessed at rest. We aimed to determine whether sphincter imaging at rest is inferior to imaging on PFMC.