Key Terms: Barium sulfate, Colonoscopy, Diverticula, Diverticulitis, Sigmoidoscopy.
Definition
A barium enema, also known as a lower GI (gastrointestinal) exam, is a diagnostic test using x-ray examination to view the large intestine (colon and rectum). There are two types of this test: the single-contrast technique, in which barium sulfate solution is injected into the rectum to gain a profile view of the large intestine; and the double-contrast (or air contrast) technique, in which air and barium sulfate are injected into the rectum.
Purpose
A barium enema may be performed to assist in diagnosing or detecting:
The double-contrast barium enema is more accurate than the single-contrast technique for detecting small polyps or tumors, early inflammatory disease, and bleeding caused by ulcers because it gives a better view of the intestinal walls.
The decision to perform a barium enema is based on the patient's history of altered bowel habits. These alterations may include diarrhea, constipation, lower abdominal pain, blood, mucus or pus in the stool. It is also recommended that this exam be used every five to 10 years beginning at age 50 to screen healthy people for colon cancer, the second most deadly type of cancer in the United States. Those who have a close relative with colon 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 to detect abnormalities.
Precautions
Although the barium enema is an effective screening method and may lead to a timely diagnosis of a variety of gastrointestinal diseases, the test may not detect all abnormalities present in the colon and rectum. In addition, the barium enema visualizes only the large intestine; the small intestine may also require examination with an upper GI series to rule out abnormalities in that area of the digestive tract. Another drawback is that intestinal gas may hinder the accuracy of test results.
Numerous studies have shown that a colonoscopy performed by an experienced gastroenterologist is a more accurate initial diagnostic tool for detecting early signs of colorectal cancer than a barium enema. Colonoscopy allows a physician to examine the entire colon and rectum for polyps. In addition, if abnormalities such as polyps are observed during the procedure, these oftenprecancerous growths may be removed during the procedure and later examined (biopsy). However, a colonoscopy almost always involves conscious sedation, while the barium enema is an unsedated procedure.
Some physicians use flexible sigmoidoscopy (proctosigmoidoscopy) plus a barium enema instead of colonoscopy. However, sigmoidoscopy only visualizes the rectum and the portion of the colon immediately above it (sigmoid colon) and does not allow the physician to remove polyps but only to obtain tissue or stool samples. In 2003, debate continued on the use of virtual colonoscopy to replace colonoscopy and perhaps barium enema for colon and rectal cancer screening. Virtual colonoscopy refers to the use of imaging, usually with computed tomography (CT) scans or magnetic resonance imaging (MRI) to produce images of the colon. Studies in late 2003 showed that virtual colonoscopy was as effective as colonoscopy for screening purposes and it offered the advantage of being less invasive and less risky. However, many physicians were unwilling to accept it as a replacement for colonoscopy, particularly since some patients might still require the regular colonoscopy as a follow-up to the virtual procedure if a polyp or abnormality is found that requires biopsy. Studies have shown virtual colonoscopy uses less radiation that barium enema and may be more beneficial for use in children in particular. As of late 2003, the American Cancer Society still recommended a barium enema examination every five years as part of regular colon cancer screening for people over age 50.
Description
To begin a barium enema, the patient lies flat on his or her back on a tilting radiographic table in order to have x rays of the abdomen taken. After being assisted to a different position, a well-lubricated rectal tube is inserted through the anus. This tube allows the physician or assistant to slowly administer the barium sulfate into the intestine. While this filling process is closely monitored, it is important for the patient to keep the anus tightly contracted against the rectal tube to help maintain its position and prevent the barium from leaking. This step is important because the test may be inaccurate if the barium leaks. A rectal balloon may also be inflated to help retain the barium. The table may be tilted or the patient 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. Upon completing this expulsion, an additional x ray is taken, and a double-contrast enema exam may follow. If this procedure is done immediately, a thin film of barium will remain in the intestine, and air is then slowly injected to expand the bowel lumen (space in the intestine). Sometimes no x rays will be taken until after the air is injected. The entire test takes about 20-30 minutes.
Preparation
In order to conduct the most accurate barium enema test, the large intestine must be empty. Thus, patients must follow a prescribed diet and bowel preparation instructions prior to the test. This preparation commonly includes restricted intake of dairy 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:
- The patient will be well draped with a gown and secured to a tilting x-ray table.
- As the barium or air is injected into the intestine, 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.
Aftercare
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 because a barium enema and the bowel preparation taken before it can be exhausting.
- Administering a cleansing enema may help to eliminate any remaining barium. The patient may have light-colored stools for 24 to 72 hours following the exam.
Risks
Although a barium enema generally is considered a safe screening test, it can cause complications in certain people. For example, patients with a rapid heart rate, severe ulcerative colitis, toxic megacolon (acute dilation of the colon that may progress to rupture), or a presumed perforation in the intestine should not undergo a barium enema. Patients with a known blocked intestine, diverticulitis, or severe bloody diarrhea may be tested with caution on the advice of a physician. Also, administering a barium enema to a pregnant woman is not advisable because of radiation exposure to the fetus.
Although the barium enema may cause minor stomach or abdominal discomfort in some people, more serious complications include:
- severe cramping
- nausea and vomiting
- perforation of the colon
- water intoxication
- barium granulomas (inflamed nodules)
- allergic reactions
These complications, however, are all very rare.
Normal Results
When the patient undergoes a single-contrast enema, the intestine is steadily filled with barium to differentiate the colon's markings. A normal result displays uniform filling of the colon. As the barium is expelled, the intestinal walls collapse. A normal result on the x ray after the barium is expelled shows an intestinal lining with a standard, feathery appearance and no abnormalities.
The double-contrast enema expands the intestine, which is already lined with a thin layer of barium; however, the addition of air displays 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.
Abnormal Results
A barium enema visualizes abnormalities appearing on a series of x rays, thus aiding in the diagnosis of a variety of gastrointestinal disorders and the early signs of cancer. However, most colon cancers occur in the rectosigmoid region, or upper part of the rectum and adjoining portion of the sigmoid colon, and are better detected with flexible sigmoidoscopy or colonoscopy.
Abnormal findings on a barium enema examination may include polyps, lesions or tumors, diverticula, inflammatory disease, such as ulcerative colitis, obstructions, or hernias. Structural changes in the intestine, gastroenteritis, and the size, position, and motility of the appendix may also be apparent.
Questions to Ask the Doctor
- How long will the test take?
- Will the test be painful?
- Is barium safe?
- Can I take my usual medications the day before the test?
- How many days will the barium be in my system?
- When will I get the test results?
Resources
Books
Fischbach, Frances Talaska. A Manual of Laboratory and Diagnostic Tests. 6th ed. Philadelphia: Lippincott Williams and Wilkins, 2000.
Periodicals
Fletcher, Robert H. "The End of Barium Enemas?" The New England Journal of Medicine 342 (June 15, 2000): 1823–1824.
Mahoney, Diana. "Virtual Colonoscopy Finds Lesions Fast: High Sensitivity, Specificity." Pediatric News January 2004: 39–41.
"Professional Organization Recommends Standard Colonoscopy Over Virtual." Biotech Week December 31, 2003: 422.
"Study Shows Virtual Colonoscopy as Effective as Traditional Colonoscopy." Biotech Week December 31, 2003.
Winawer, Sidney J., Edward T. Stewart, Ann Zauber, et al. "A Comparison of Colonoscopy and Double-Contrast Barium Enema for Surveillance After Polypectomy." The New England Journal of Medicine 342 (June 15, 2000): 1766–1772.
Zoorob, Roger, Russell Anderson, Charles Cefalu, and Modamed Sidari. "Cancer Screening Guidelines." American Family Physician 63 (March 15, 2001): 1101–1112.
Organizations
American Cancer Society. 1599 Clifton Road, NE, Atlanta, GA 30329-4251. Phone: 1-800-ACS-2345. .
American College of Gastroenterology. 4900 B South 31st Street, Arlington, VA 22206. Phone: 703-820-7400. Health Hotline: 1-800-978-7666. .
American College of Radiology. .
—Beth Kapes; Teresa G. Odle
