Patient Instructions for Anorectal Physiology (ARP) Testing
Anal Manometry
Anal manometry is performed to evaluate patients with constipation and/or fecal incontinence. Anal manometry measures pressures of the anal sphincter muscles and the sensation in the rectum. The test takes approximately 30 minutes. 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.. During the test the nurse asks the person to squeeze or relax the anal muscle. 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. The doctor may perform two other tests. First, an anal EMG which is a test to evaluate the nerve supply to the anal muscle. In addition an ultrasound of the anal sphincter may be performed. After the examination, you may drive yourself home, eat and go about your normal activities.
Anal Sphincter EMG (Electromyography)
EMG measures the electrical activity in the pelvic floor (puborectalis) muscle. In constipated patients, an EMG is performed using postage stamp sized skin sensor applied near the anal opening. The patient 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.
In incontinent patients, the nerve that controls the sphincter muscle may have been damaged. In order to test for this, a fine sensor attached to the tip of the gloved examining finger of the physician is inserted into the anal canal. A gentle electrical impulse is delivered which most patients cannot feel. The time it takes for the muscle to respond is recorded and the procedure repeated on the other side.
Rectal Ultrasound
This painless exam involves inserting a small probe into the anal canal and using sound waves, a picture of the anal sphincter is generated. This reveals any potential abnormalities or injury in the muscle.
Risks:
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.