Endosonography of the anal sphincters: Normal anatomy and comparison with manometry

Abstract

To determine the normal anal anatomy in vivo, anal endosonography and manometry were performed in 93 nulliparous females, and endosonography alone in 21 healthy males. Endosonography did not reveal any plane of cleavage between the components of the external anal sphincter, though a changing pattern at different levels conforming to a trilaminar arrangement was apparent. The deep (proximal) aspect of the external sphincter was annular in 72% of females and 76% of males. The superficial external sphincter was elliptical in 76% and 86%, the subcutaneous part conical in 56% and 57%, respectively. The external sphincter was shorter anteriorly in females. Aberrant insertions from the external sph..