Virtual Colon Scans Eliminate Much of the Discomfort of This Important Test
When Elsye Lupino was checked for colon cancer five years ago, she was sedated intravenously and had to stay at the hospital for most of the day and be driven home. Two weeks ago, after her colonoscopy, the Brooklyn, N.Y., bookkeeper, 56, sipped a cup of coffee at the doctor's office and then headed to work. This time, instead of a conventional colonoscopy, in which a 5-foot-long probe is snaked up the colon, Lupino had a virtual version in which the colon is scanned noninvasively. "It was much easier, quicker. You're in and out in two hours, tops," she says.
Devices used in virtual colonoscopy have been approved by the Food and Drug Administration for about two years. Like the conventional colonoscopy, some of these procedures require patients to go on a liquid diet and take laxatives beforehand. And the tests remain expensive. Yet some of the latest scans are faster, expose the patient to less radiation, or require less preparation than earlier procedures, which doctors hope will lead to more screening. Fewer than 20 percent of those 50 and over and those with a family history of polyps and colon cancer--who should be tested--actually get screened, in part because of discomfort. "People may be much more willing to get screened if it involves no bowel preparation with laxatives. I think it's going to become a principal screening tool," says Stanley Benjamin, chief of the division of gastroenterology at Georgetown University Hospital in Washington, D.C.
Sophisticated scan. Colon cancer is the nation's third most common cancer, but it can be averted if polyps, tiny precancerous and cancerous growths on the wall of the colon, are detected early and removed. In a conventional colonoscopy, doctors search for polyps with a kind of long, flexible periscope. In virtual colonoscopy, the view is from the outside. A scanner takes hundreds of X-rays, or slices, each at a different angle. Sophisticated software combines the data to produce a 3-D image of the colon.
The scans are detailed enough, according to some studies, to reliably reveal polyps as small as 6 millimeters in diameter. Doctors find microscopic indications of cancer in polyps as small as 5 millimeters but don't classify a polyp as a cancer risk until it reaches 1 centimeter. A virtual scan allows physicians to explore crevices a colonoscope can't always probe. The discomfort and slight risks of conventional colonoscopy--bowel injury or a reaction to the sedative--are eliminated, though some unpleasant preliminaries may remain.
In one system, introduced last fall by Viatronix, patients no longer must eat a completely liquid diet or wash out their bowels with strong laxatives before. Instead, they are asked to eat low-residue foods like Jell-O, potato chips, and nutritional drinks for two days. Before the test, a patient downs contrast drinks that bind to the liquid and residual material in the colon. In the scanning room, a small air pump is inserted into the rectum and fills the colon with carbon dioxide, expanding it for imaging. After the 10-minute scan, the software digitally removes the contrast-labeled food and drink from the X-rays, creating a clean image of the colon for doctors to examine.
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