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.
To conduct the most accurate barium enema test, the patient must follow a prescribed diet and bowel preparation instructions before the test. This preparation commonly includes restricted intake of dairy products and a liquid diet for 24 hours before 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 to help empty the bowel and be asked to give themselves a cleansing enema.
Patients should follow several steps immediately after undergoing a barium enema, including:
A barium enema may be performed for a variety of reasons. One reason may be to help in screening for or diagnosing colon and rectal cancer (colorectal cancer). 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 be confirmed by the barium enema. The double-contrast barium enema is an effective method for detecting small tumors, early inflammatory disease, and bleeding caused by ulcers. Colonoscopy, which uses a thin, flexible, fiber-optic device to visualize the colon and rectum, has largely replaced the barium enema in diagnosing these diseases in many countries; however, colonoscopy is more expensive to perform.
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 stool. Colorectal cancer screening is recommended for healthy people over age 50 every five to 10 years. In 2010, colorectal cancer was the second leading cause of cancer-related death 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. In the United States, this screening is most often done by a colonoscopy, although it can also be done by using a barium enema.
Twenty-four hours before the barium enema, the patient will begin following a bowel-cleansing regimen that involves restricted diet and administration of laxatives. To begin a barium enema, the doctor will have the patient lie on their back facing upward (supine) on a tilting radiographic table so that x rays 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 pre-procedure 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 out.This step is emphasized to the patient because inaccuracy may occur if the barium leaks. A rectal balloon also may 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. The patient 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.
As the barium fills the colon, x rays of the abdomen are taken to distinguish significant findings. There are several ways to perform a barium enema. In one method, shortly after filling, the rectal tube is removed and the patient expels as much of the barium as possible. In another method, the tube will remain in place, and the barium will move through that tube. A thin film of barium remains in the intestine, and then, in a double contrast enema, air is slowly injected through the rectum to expand the bowel lumen. Usually no x-ray films will be taken until after the air is injected. Multiple films generally are obtained by a radiologist; then, additional films are made by a technologist.
While a barium enema is considered a safe screening and diagnostic test, it can cause complications in certain people. The following indications should be kept in mind before a barium enema is performed:
When patients undergo single-contrast enemas, their intestines are steadily filled with barium to differentiate markings of the colon. 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. In a healthy patient, the walls will have a uniform, standard appearance.
A barium enema will show abnormalities 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 sigmoidoscopy. Further, an enema can identify other early signs of cancer.
Identification of polyps, diverticulosis, and inflammatory disease such as diverticulitis and ulcerative colitis may be made through a barium x ray. Some cases of acute appendicitis also may be apparent by viewing this x ray, although acute appendicitis is usually diagnosed clinically, or by computed tomography (CT) scan.