Normally, when stool enters the rectum, the anal sphincter muscle tightens to prevent passage of stool at an inconvenient time. If this muscle is weak or doesn’t contract in a timely way, incontinence (leakage of stool or feces) may occur. On the other hand, when a person pushes or bears down to have a bowel movement, the anal sphincter muscles relax. This causes the pressures to decrease, allowing evacuation of stool. If the sphincter muscles tighten when pushing, this could lead to constipation.
What to Expect With You Have an Anorectal Manometry Test
An anorectal manometry test measures the pressure of the anal sphincter muscles, the sensation in the rectum and the neural reflexes needed for normal bowel movements.
An anorectal manometry test takes about 30 minutes. During the test, you will lie on your side. A doctor will insert a small, flexible catheter tube about the size of a thermometer with a balloon at the end into the rectum. The catheter tube is connected to a machine that measures pressure. The small balloon attached to the catheter may be inflated to assess normal reflex pathways. You may be asked to squeeze, relax or push at various times. The anal sphincter muscle pressures are measured during each of these maneuvers.