Morphology of the region anterior to the anal canal in males: visualization of the anterior bundle of the longitudinal muscle by transanal ultrasonography

Purpose The anterior bundleof the longitudinal muscle in the region anterior to the anal canalin males has been described, although the anatomical details remain unclear. The present study was undertaken to clarify the precise morphology of the anterior bundleof the longitudinal muscle and its relationship to the surrounding structures, and to visualize the anterior bundleof the longitudinal muscle via transanal ultrasonography.