Examination of the function of the distal colon and anal sphincter muscles is a test for patients with constipation or fecal incontinence to detect abnormalities in the muscles controlling defecation. It measures the strength of the sphincter muscles, the sensation of the anus, and the response of the anal sphincter muscles during contraction or straining to defecate.
Did you know? How the distal colon and anal sphincter work
The distal colon and anal sphincter consist of special muscles that work together to perform the function of defecation. Normally, when stool passes into the anus, the distal colon contracts. When it is the appropriate time and the urge to defecate arises, the anal sphincter muscles relax to allow stool to pass out. Conversely, when defecation is not desired, the anal sphincter muscles contract to prevent stool leakage. If the sphincter muscles are weak or unable to contract properly, or if the sensation in the anus is abnormal, it can result in stool leakage or inability to hold stool.
What can the examination of the distal colon and anal sphincter function reveal?
This test provides information about the mechanism of the muscles controlling defecation, measures the strength of the sphincter muscles, the relaxation of the anal sphincter during defecation, and the sensation of the anus. It is useful in treating chronic constipation caused by improper straining or by spasm or failure to relax the anal sphincter during defecation, as well as fecal incontinence.
Preparation before the examination
- Perform an enema once 2 hours before bedtime and another enema on the morning of the examination 2 hours before the test
- Fast from food and drink for at least 2 hours before the examination
- You may take medications as usual but at least 2 hours before the examination
- Urinate before the examination
- Inform the doctor and staff if you are allergic to latex
Procedure for examining the function of the distal colon and anal sphincter muscles
The examination takes about 30 minutes and is painless, so hospitalization is not required. Before the test, the patient may be asked to change into a hospital gown and provide a brief medical history. During the test, the patient lies on their side. A probe about the size of a milk carton straw with a small balloon at the tip is inserted about 5 centimeters into the anus. Water is then injected into the balloon to observe the response of the anus and measure the sensation of the distal colon. The other end of the probe is connected to a pressure measuring device. During the test, the patient should cooperate by contracting, relaxing, and straining periodically to observe the function of the sphincter muscles. After the test, the patient can go home and resume normal activities. Additionally, two other tests may be performed: colonic transit study and balloon expulsion timing from the anus.
- Colonic transit study
This test evaluates the overall movement of the colon. The patient swallows a non-absorbable, non-toxic radiopaque substance. X-rays of the abdomen are taken 3 and 5 days later to observe the movement of the substance, which simulates stool movement in the colon to assess its speed. The patient only undergoes two X-ray images, so the radiation exposure is very low.
- Balloon expulsion timing from the anus
In this test, a small balloon is inserted into the anus, then filled with 50 milliliters of water to inflate it. The patient is then asked to strain as if defecating in a bathroom, and the time taken to expel the balloon is recorded.
Possible complications from the examination
The examination of the anal sphincter muscle function is safe and painless with very low risk. The possible complication is “bleeding,” which mostly occurs from hemorrhoids, is not severe, and can be treated.
If abnormalities are found… here is the correct treatment!
Abnormalities in the function of the muscles controlling defecation cannot be treated with laxatives but can be treated with muscle training and normalization of anal sensation (biofeedback therapy). This helps patients learn how to properly control these muscles, improving symptoms of constipation and fecal incontinence.
