What is anorectal manometry?
Anorectal manometry (ARM) is a noninvasive procedure to evaluate the function of the
rectal and anal muscles. This group of muscles, called the anorectal sphincter, controls
how stool is released from your body. Anorectal manometry can help determine if these
muscles are too loose, too tight or are not engaging at the right moment. This test
measures the pressures created by the muscles, the sensation in the rectum (the
passageway between the large intestine and the anus), and the neural reflexes
necessary for normal bowel movements.
Who may need anorectal manometry?
Having a bowel movement requires cooperation between specialized muscles and
nerves in the rectum and anal canal. Normally, when stool enters the rectum, the anal
sphincter muscles tighten to prevent passage of stool until you can get to a toilet. If
these muscles are weak or do not contract in a timely way, fecal incontinence (leakage
of stool) may occur. Similarly, when you push to have a bowel movement, the anal
sphincter muscles relax to allow stool to exit. If they tighten instead, this could contribute
to constipation.
Anorectal manometry tests these functions and helps diagnose conditions such as fecal
incontinence and constipation. If you have ongoing problems with bowel movements,
your doctor may recommend anorectal manometry.
Anorectal manometry can also be used to evaluate people with:
- Malformations or injuries of the anus or rectum affecting nearby nerves or
muscles. - Hirschsprung’s disease, a condition that is present at birth, and affects the
muscles of the bowel. - Irritable bowel syndrome, a condition that involves both diarrhea and
constipation. - Rectal cancer if it was treated with procedures that affect the function of
anorectal muscles.
What happens during anorectal manometry?
Anorectal manometry is a fairly simple test and does not require anesthesia. The
equipment to perform this test usually includes:
- A catheter with a balloon on the end that gets inserted into the anus and rectum.
- A device connected to the catheter that allows a technician to change the
pressure in the balloon by inflating and deflating it, usually with air. - Computer software connected to the pressure device that controls the test
settings and records data from the balloon.
The test usually takes about 30 minutes. Before the procedure, you will need to make
sure your digestive tract is empty. Your doctor may recommend using one or more
over-the-counter enemas at home before the test.
- You will need to undress from the waist down or change into a hospital gown, as
instructed by the technician or nurse performing the test. A technician will explain
the procedure, take a brief health history and answer your questions. - You lie down on your left side and bring your knees up into a fetal position.
- Before starting the anorectal manometry test, the technician may first perform a
digital rectal exam by inserting a gloved finger into the anus to feel for
abnormalities. - A small, flexible, lubricated tube, about the size of a thermometer, with a deflated
balloon at the end is inserted into the rectum. The tube is connected to a
machine that measures pressure. - The technician will position the balloon at various depths inside the rectum and
take several benchmark pressure readings. - The technician will then inflate the balloon to a certain size and ask you to
squeeze, relax, push or cough for brief intervals of time. These activities are
repeated with different balloon sizes or positions in the rectum. The anal
sphincter muscle pressures are measured each time. - To squeeze, you tighten the sphincter muscles as if trying to prevent anything
from coming out. Coughing also contracts your anal sphincter. - To push or strain, you bear down as if you are trying to have a bowel movement.
- The technician might also ask you if the sensation in your rectum changes with
different balloon sizes. You will need to say when it feels like you need to have a
bowel movement. - When the test is finished, the technician deflates and removes the balloon.
- After the examination, you may drive yourself home and go about your normal
activities.
Anal Manometry Test Results
Test results can help your doctor identify the cause of constipation or incontinence and
inform a treatment plan.
For instance, the test may reveal weak anal sphincter muscles or poor sensation in the
rectum that can contribute to fecal incontinence. These problems can be treated.
Biofeedback techniques using anal manometry and special exercises of the pelvic floor
muscles can strengthen the muscles and improve sensation.
Test results may show that the anal sphincter muscles do not relax appropriately when
you are pushing to have a bowel movement, which may cause constipation. These
muscles, too, can be retrained with biofeedback techniques.
Risks and Complications of Anorectal Manometry
Anorectal manometry is a safe, low-risk procedure and complications are rare.
Equipment failure is a remote possibility. People who are allergic to latex should inform
the nurse or technician before the test.