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Colonoscopy Test for Colon Cancer May Be More Effective

WebMD Health News

June 14, 2000 -- Even among people who've never had one, the term barium enema can inspire fear. Long used to screen for colon cancer, barium enemas have recently fallen out of favor with those who prefer an imaging method called colonoscopy. And a new study shows that, in people with a history of colon growths, or polyps, colonoscopies may be better than barium enemas at detecting problems.

The research comes amid continuing debate about which technique is better for follow-ups after the recommended colon cancer screening performed in all people over age 50. Although this study, published in the New England Journal of Medicine, does not address whether colonoscopies also should be used for the initial screening, some experts, including the study's author, tell WebMD that it should.

Sidney J. Winawer, a gastroenterologist at Memorial Sloan-Kettering Cancer Center in New York, tells WebMD that barium enemas are no longer practical. But "colonoscopy for cancer screening presents a unique activity -- we can find polyps and remove them, and actually prevent cancer."

Both barium enemas and colonoscopy involve making images of the colon, and both have the same goal -- finding polyps, some of which may become cancerous over time. With both procedures, patients must eat a special diet or drink liquids to empty the bowel the day before to make the tests more accurate.

In a colonoscopy, a specialist uses a small tube to introduce air into the bowel in order to see the polyps. Its advantage is that physicians can remove the polyp as soon as it is discovered. But there is a small risk of tearing the bowel during the procedure, and the patient must be sedated, which can cause side effects. This procedure also is more costly than a barium enema.

A few months ago, broadcast journalist Katie Couric underwent a colonoscopy on television to call attention to colon cancer, which killed her husband.

In barium enemas, a radiologist introduces the element barium into the bowel, along with air. No sedation is required. If polyps that should be removed are detected during a barium enema, a colonoscopy usually is required.

Although there is no dispute that people over age 50 should be screened for colon cancer, the medical community has been split over which methods are best. In addition to barium enemas and colonoscopies, other recommended screening tests for colon cancer include a fecal occult test, which can detect blood in the stool, and sigmoidoscopy, which is less invasive than a colonoscopy.

The study by Winawer and his colleagues is the first to match one method against the other to see which is better at detecting polyps. The researchers performed both barium enemas and colonoscopies on more than 500 people, and also reviewed the findings on more than 300 other people who had only colonoscopies. All the patients previously had polyps. Colonoscopies found three times as many smaller polyps and twice as many larger ones as barium enemas did.

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