Constipation Home > Barium Enema X-rays and Other Tests for Constipation

Diagnosing Constipation: Anorectal Function Tests

Anorectal function tests diagnose constipation caused by abnormal functioning of the anus or rectum. One such test, known as anorectal manometry, evaluates the function of anal sphincter muscle. For this test, a catheter or air-filled balloon is inserted into the anus and then slowly pulled back through the sphincter muscle to measure muscle tone and contractions.
Defecography is an x-ray of the anorectal area that:
  • Evaluates how completely stool is eliminated
  • Identifies anorectal abnormalities
  • Evaluates rectal muscle contractions and relaxation.
During the defecography exam, the doctor fills the rectum with a soft paste that is the same consistency as stool. The patient sits on a toilet positioned inside an x-ray machine and then relaxes and squeezes the anus to expel the paste. The doctor studies the x-rays for anorectal problems that occurred as the paste was expelled.

Diagnosing Constipation: Barium Enema X-ray

A barium enema exam involves viewing the rectum, colon, and lower part of the small intestine to locate any problems. This part of the digestive tract is known as the bowel. This test may show intestinal obstruction and Hirschsprung's disease, which is a lack of nerves within the colon.
The night before the test, bowel cleansing (also called bowel prep) is necessary to clear the lower digestive tract. The patient drinks a special liquid to flush out the bowel. A clean bowel is important, because even a small amount of stool in the colon can hide details and result in an incomplete exam.
Because the colon does not show up well on x-rays, the doctor fills it with barium, a chalky liquid that makes the area visible. Once the mixture coats the inside of colon and rectum, x-rays are taken. These x-rays reveal the shape and condition of the colon and recturm. The patient may feel some abdominal cramping when the barium fills the colon, but usually feels little discomfort after the procedure. Stools may be a whitish color for a few days after the exam.
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Last reviewed by: Arthur Schoenstadt, MD
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