Anorectal manometry (also called rectal manometry, ARM, or AM) - Anorectal manometry is a test that evaluates bowel function in patients suffering from fecal incontinence or chronic constipation. The technique uses a small balloon in the rectum to distend the rectum and looks at: the strength of the anal sphincter muscles, sensations of stool in the rectum, reflexes that govern the bowel, and movements of the rectal and anal muscles. See Figure 1 showing a balloon.
Anorectal manometry is a very important diagnostic tool used in the full and proper assessment of fecal incontinence and chronic constipation.
The anal and the rectal area contains specialized muscles that regulate the proper passage of bowel movements. Normally, when stool enters the rectum, the anal sphincter muscle tightens to prevent passage of stool at an undesirable time. If this muscle is weak or does not contract in a timely way, incontinence (leakage of stool) may occur.
Sphincter muscles can be weakened for many reasons, and some are 1) tearing or partial tearing of the sphincter muscle, 2) spinal cord injuries, and 3) prior surgery complications.
Normally, when a person pushes or bears down to have a bowel movement, the anal sphincter muscles relax. This will cause the pressures to decrease allowing evacuation of stool. If the sphincter muscles tighten when pushing, this could contribute to constipation. Anal manometry measures how strong the sphincter muscles are and whether they relax as they should during passing a stool. It provides helpful information to the doctor in treating patients with fecal incontinence or severe constipation.