Anorectal Manometry

What is Anorectal Manometry?

Anorectal manometry is performed to evaluate patients with constipation and/or fecal incontinence. Anorectal manometry measures pressures of the anal sphincter muscles and the sensation in the rectum. The anal sphincter is a ring of muscles at the opening to the outside of your body. The rectum is the last part of of the large intestine.

Why is Anorectal Manometry Done?

The anal and rectal area contains specialized muscles that are helpful in regulating proper passage of bowel movements. 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 does not contract in a timely way, incontinence (leakage of stool) may occur.

Normally, when a person pushes or bears down to have a bowel movement, the anal sphincter muscles relax. This will cause the pressure 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 the passing of a stool. It provides helpful information to the doctor in treating patients with fecal incontinence or severe constipation. There are many causes of fecal incontinence. Weak anal sphincter muscles or poor sensation in the rectum can contribute to fecal incontinence. If these abnormalities are present, they can be treated. Biofeedback techniques using anal manometry and special exercises of the pelvic floor muscles can strengthen the muscles and improve sensation. This can help treat fecal incontinence.

There are many causes of constipation. Some involve sluggish movement through the whole colon, whereas others involve the anal sphincter muscles. In some patients with constipation, the anal sphincter muscles do not relax appropriately when bearing down or pushing to have a bowel movement. This abnormal muscle function may cause a functional type of obstruction. Muscles that do not relax with bearing down can be retrained with biofeedback techniques using anal manometry.

How Does One Prepare for Anorectal Manometry?

Patients should follow the following instructions:

•    Purchase two Fleet enemas from the drugstore
•    Administer one enema the night before the exam, at least two hours prior to bedtime
•    Administer the second enema early on the morning of the exam
•    Take your regular medications on the morning of the procedure (e.g. for blood pressure)
•    You may eat the day of the test
•    You may take schedule medications at least 2 hours prior to the study with small sips of water
•    Please empty your bladder prior to the exam
•    You may drive yourself home after the test since no sedation is involved
•    Please read all the instructions and directions prior to appointment

How is Anorectal Manometry Performed?

The test takes approximately 30 minutes and is not a painful procedure. Patients will be asked to change into a hospital gown. A nurse will review the procedure with you, take a brief health history and answer any questions you may have. The person then lies on his/her left side. A small, flexible tube, about the size of a thermometer, is inserted into the rectum. A tiny amount of water drips into the tube while it is connected to a machine that measure pressure. During the test the nurse asks the person to squeeze, relax, and push. The anal sphincter muscle pressures are measured during each of these maneuvers. To squeeze, the person tightens the sphincter muscles as if trying to prevent anything from coming out. To push, the person strains down as if trying to have a bowel movement. After the examination, you may drive yourself home, eat and go about your normal activities.

What are the Risks Associated with Anorectal Manometry?

Anorectal manometry is a safe, low risk procedure and is unlikely to cause any pain. Complications can occur, but are rare: it is possible that a perforation (tearing) or bleeding of the intestinal wall could occur. Equipment failure is extremely unlikely, but does remain a remote possibility.