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.
Give yourself a Fleet enema 2 hours prior to your study (You can get the Fleet enema from a pharmacy or supermarket).
You should not eat anything during the two hours prior to the procedure. If you are diabetic, this may involve adjusting your diabetic medications.
You may take scheduled medications at least 2 hours prior to the study with small sips of water
The test takes approximately 30 minutes. You 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 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 measures 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. The doctor may perform two other tests. First, an anal EMG which is a test to evaluate the nerve supply to the anal muscle. Second, measurement of the time to expel a balloon from the rectum. After the examination, you may drive yourself home, eat and go about your normal activities.
Anal sphincter EMG is recorded with a small sponge electrode or plug placed in the anal canal. The person relaxes squeezes and pushes. A computer records sphincter muscle electrical activity. Anal sphincter electromyography confirms the proper muscle contractions during squeeze and muscle relaxation during push. In people with non-relaxing puborectalis, the tracing of electrical activity gets bigger, instead of smaller, during a push. Normal anal EMG activity with low anal squeeze pressures on manometry may indicate a torn sphincter muscle that could be repaired.
For this procedure, a small balloon is inserted into the rectum. The patient goes to the bathroom and tries to defecate (expel) a small balloon in the rectum.
What does one learn from anorectal manometry?
Ordinarily, the sphincter muscle tightens, and the anal canal pressures increase when the person tries to squeeze. When the person stops squeezing, the muscles should relax, and pressures return to baseline. When the person pushes, as if having a bowel movement, the sphincter muscles should stay relaxed. This will cause the pressures to stay the same as during rest, or to decrease slightly. If the pressures increase during a push, this may be a sign that the sphincter muscles tighten when pushing. This tightness could contribute to constipation. Anal manometry shows how strong the sphincter muscles are and if they relax as they should during rectal emptying. Weak muscles that still tighten some can be strengthened with special exercise and treatments. Muscles that do not relax with a push can also be retrained. This is called Pelvic Muscle Retraining and is discussed later. If the muscles are very weak, some constipation operations may be modified. If a person with colonic inertia has weak sphincters, then to prevent incontinence, the colon may not be shortened as much.
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