Manometry, profilometry, and endosonography: normal physiology and anatomy of the anal canal in healthy children.

Normal and manometric and profilometric values and normal endosonographic features of the anal canal are required for evaluation of pathological conditions such as slow-transit constipation, anorectal outlet obstruction, and Hirschsprung's disease, status after surgery for imperforate anus, and other anal abnormalities. Anorectal manometry, profilometry (rapid-pull-through, three-dimensional, eight-channel radial manometry), and endosonography were carried out in 13 healthy children. A significant correlation was demonstrated between conventional manometric and profilometric maximal squeeze pressure of the external anal sphincter (EAS). However, the maximal and resting tone of the sphincter complex in profilometry was twice as high as in manometry due to reflexive contraction of a pelvic floor muscle, probably the EAS. With profilometry a positive correlation was found between age and sphincter length. Endosonographically assessed thickness of the EAS, puborectal muscle, and levator ani complex showed a significant correlation with age. However, no correlation was demonstrated between age and internal anal sphincter thickness. Thus, the development of the essential structures of the anal canal in children is age dependent. In addition, these measurements of normal physiology and anatomy of the anal canal provide the basis for detecting pathological conditions of the anorectal region in children.