A double-contrast barium enema is an imaging technique that enables doctors to use X-ray scans to evaluate the colon for signs of illness. Symptoms such as a change in bowel habits or unusual stools can lead a doctor to order this test to differentiate among several conditions. Avoiding an invasive procedure like surgery is an important benefit of using a double-contrast barium enema, but the test is becoming less common because of its limitations. This technique requires several days of preparation to empty the colon so that the clearest possible image can be obtained.
A double-contrast barium enema is a two-step process wherein the first step is to flood the colon with a solution containing barium sulfate through a tube inserted into the anus. The barium clings to the surface of the colon wall, and the excess is allowed to drain out of the colon. The second step is to slowly pump air into the colon. The barium acts as a contrast agent because it blocks X-rays and allows the colon to be seen separately from the surrounding soft tissues. The air provides a second contrast between the wall of the colon and the interior space, or lumen.
Unusual periods of diarrhea or constipation, blood, pus, or mucus in the stool, or abdominal pain are symptoms that may indicate the need for this test. The colon X-rays created with a double-contrast barium enema look for ulcers, inflammation, and colorectal cancer. They can also detect benign polyps and diverticula, i.e., pockets in the wall of the intestine.
This X-ray technique allows a doctor to get a general picture of the health of the colon while being fairly non-invasive. Although for most people a double-contrast barium enema is considered safe enough to be used routinely, it is not recommended for patients with some conditions such as ulcerative colitis or a perforated intestine. Another limitation is that, unlike a colonoscopy procedure, the doctor is unable to remove polyps or cancerous growths or to correct diverticula during this test. The associated risks are very rare but include perforation, water intoxication, and allergic reaction.
For a period of one to three days before a double-contrast barium enema is performed, the patient will be asked to consume only clear fluids. On the day before the procedure, strong laxatives may be given or the patient may be asked to self administer a standard enema at home. This preparation is meant to remove as much fecal material as possible so that stools will not be mistaken for polyps.