Constipation other imaging findings
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American Roentgen Ray Society Images of Constipation |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Other Imaging Findings
Colorectal Transit Study
This test shows how well food moves through the colon. The patient swallows capsules containing small markers that are visible on an x ray. The movement of the markers through the colon is monitored by abdominal x rays taken several times 3 to 7 days after the capsule is swallowed. The patient eats a high-fiber diet during the course of this test.
Anorectal Function Tests
These tests diagnose constipation caused by abnormal functioning of the anus or rectum—also called anorectal function.
- Anorectal manometry evaluates anal sphincter muscle function. For this test, a catheter or air-filled balloon is inserted into the anus and slowly pulled back through the sphincter muscle to measure muscle tone and contractions.
- Balloon expulsion tests consist of filling a balloon with varying amounts of water after it has been rectally inserted. Then the patient is asked to expel the balloon. The inability to expel a balloon filled with less than 150 mL of water may indicate a decrease in bowel function.
Defecography
Defecography is an x ray of the anorectal area that evaluates completeness of stool elimination, identifies anorectal abnormalities, and evaluates rectal muscle contractions and relaxation. During the 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, 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.
Barium Enema X Ray
This exam involves viewing the rectum, colon, and lower part of the small intestine to locate problems. This part of the digestive tract is known as the bowel. This test may show intestinal obstruction and Hirschsprung 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 the colon and rectum, x rays are taken that show their shape and condition. The patient may feel some abdominal cramping when the barium fills the colon but usually feels little discomfort after the procedure. Stools may be white in color for a few days after the exam.
Rectal Balloon Expulsion Test
Rectal balloon expulsion test is a simple procedure, that evaluates a patient’s ability to evacuate a water-filled balloon. It can be performed in isolation or in conjunction with anorectal manometry.
The preferred approach is to quantify the time required to expel a rectal balloon in the seated position and the normal values range from less than 1 minute to up to 5 minutes. Alternatively, the magnitude of additional passive forces needed to expel the balloon in the lateral decubitus position can be measured if spontaneous evacuation is not possible. Depending on the technique, patients with pelvic floor dysfunction require more time or more external traction to expel the balloon.