A barium enema, also known as a lower GI (gastrointestinal) exam, is a test that uses x-ray examination to view the large intestine. There are two types of tests: the single-contrast technique, where barium sulfate is injected into the rectum to gain a profile view of the large intestine, and the double-contrast (or "air contrast") technique, where air and barium are inserted into the rectum.
A barium enema may be performed for a variety of reasons. One reason may be to help in the diagnosis of colon and rectal cancer (or colorectal cancer), and inflammatory disease. Detection of polyps (benign growths in the tissue lining the colon and rectum), diverticula (pouches pushing out from the colon), and structural changes in the large intestine can also be confirmed by the barium enema. The double-contrast barium enema is the best method for detecting small tumors (such as polyps), early inflammatory disease, and bleeding caused by ulcers.
A doctor's decision to perform a barium enema is based on a patient's history of altered bowel habits. These can include diarrhea, constipation, lower abdominal pain, or patient reports of blood, mucus, or pus in the stools. It is recommended that healthy people have a colorectal cancer screening colonoscopy every five to 10 years, because this form of cancer is the second most deadly type in the United States. Those who have a close relative with colorectal cancer, or who have had a precancerous polyp, are considered to be at an increased risk for the disease and should be screened more frequently by their doctor for possible abnormalities.
To begin a barium enema, the doctor will have the patient lie with their back down on a tilting radiographic table so that x rays can of the abdomen can be taken. The film is then reviewed by a radiologist, who assesses if the colon has been adequately cleansed of stool during the prep process. After being assisted into a different position, a well-lubricated rectal tube is inserted through the anus. This tube allows the physician or the assisting health care provider to slowly administer the barium into the intestine. While this filling process is closely monitored, the patient must keep the anus tightly contracted against the rectal tube so that the position is maintained and the barium is prevented from leaking. This step is emphasized to the patient because inaccuracy may occur if the barium leaks. A rectal balloon may also be inflated to help the patient retain the barium. The table may be tilted or the patient may be moved to different positions to aid in the filling process.
As the barium fills the intestine, x rays of the abdomen are taken to distinguish significant findings. There are many ways to perform a barium enema. One way is that shortly after filling, the rectal tube is removed and the patient expels as much of the barium as possible. Alternatively, the tube will remain in place, and the barium will move through that tube. A thin film of barium remains in the intestine, and air is then slowly injected through the rectum and to expand the bowel lumen. Usually no films will be taken until after the air is injected. Multiple films are generally obtained by a radiologist; then, additional films are made by a technologist.
To conduct the most accurate barium enema test, the patient must follow a prescribed diet and bowel preparation instructions prior to the test. This preparation commonly includes restricted intake of diary products and a liquid diet for 24 hours prior to the test, in addition to drinking large amounts of water or clear liquids 12–24 hours before the test. Patients may also be given laxatives , and asked to give themselves a cleansing enema.
In addition to the prescribed diet and bowel preparation prior to the test, the patient can expect the following during a barium enema:
- They will be well draped with a gown as they are placed on a tilting x-ray table.
- As the barium or air is injected into the intestine, they may experience cramping pains or the urge to defecate.
- The patient will be instructed to take slow, deep breaths through the mouth to ease any discomfort.
Patients should follow several steps immediately after undergoing a barium enema, including:
- Drinking plenty of fluids to help counteract the dehydrating effects of bowel preparation and the test.
- Taking time to rest. A barium enema and the bowel preparation taken before it can be exhausting.
- A cleansing enema may be given to eliminate any remaining barium. Lightly colored stools will be prevalent for the next 24–72 hours following the test.
While a barium enema is considered a safe screening test used on a routine basis, it can cause complications in certain people. The following indications should be kept in mind before a barium enema is performed:
- Those who have a rapid heart rate, severe ulcerative colitis, toxic megacolon, or a presumed perforation in the intestine should not undergo a barium enema.
- The test can be performed cautiously if the patient has a blocked intestine, ulcerative colitis, diverticulitis, or severe bloody diarrhea.
- Complications that may be caused by the test include perforation of the colon, water intoxication, barium granulomas (inflamed nodules), and allergic reaction. However, these conditions are all very rare.
When patients undergo single-contrast enemas, their intestines are steadily filled with barium to differentiate markings of the colon markings. Normal results display uniform filling of the colon.
As the barium is expelled, the intestinal walls collapse. A normal result on the x ray after defecation will show the intestinal lining as having a standard, feathery appearance.
The double-contrast enema expands the intestine, which is already lined with a thin layer of barium, using air to display a detailed image of the mucosal pattern. Varying positions taken by the patient allow the barium to collect on the dependent walls of the intestine by way of gravity.
A barium enema allows abnormalities to appear on an x ray that may aid in the diagnosis of several different conditions. Most colon cancers occur in the rectosigmoid region, or on the upper part of the rectum and adjoining portion of the sigmoid colon. However, they can also be detected with a proctosigmoidoscopy (usually referred to as a sigmoidoscopy ). Further, an enema can identify other early signs of cancer.
Identification of polyps, diverticulosis, and inflammatory disease (such as diverticulitis and ulcerative colitis) is attainable through a barium x ray. Some cases of acute appendicitis may also be apparent by viewing this x ray, though acute appendicitis is usually diagnosed clinically, or by CT scan.
Gazelle, G. "Screening for Colorectal Cancer." Radiology 327 (May 2000)
Rubesin, S. "Double Contrast Barium Enema Examination Technique." Radiology 642 (June 2000).
American Cancer Society. 1599 Clifton Rd., NE, Atlanta, GA 30329-4251. (800) 227-2345. http://www.cancer.org .
Beth A. Kapes
Lee A. Shratter, M.D.