Colon scans reveal heart risk

Science News, Dec 18, 2004

Virtual colonoscopy, a scanning procedure designed to spot cancer-related growths in the colon, may offer a side benefit: identifying heart attacks that are waiting to happen. Radiologists at the Mayo Clinic in Rochester, Minn., have found that ominous circulation-hampering calcium deposits in an abdominal artery are visible on colon scans.

Jesse A. Davila, now at the Mayo Clinic's facility in Jacksonville, Fla., and his colleagues reviewed 480 patients' test results from computed tomography (CT) scans. Physicians had ordered the scans to examine abnormalities in the patients' colons, but the images show a full cross-section of the abdomen and so also depict the main artery that carries blood to the lower trunk and legs.

The researchers used a software program to translate the visible signs of calcium in the CT image into quantitative measures of how much calcium had accumulated in the artery. They suspect that calcium buildup there reflects a similar accumulation in the heart's coronary arteries, where a blockage can occur (SN:9/13/03,p. 174).

The patients showed no symptom of heart disease at the time of their virtual colonoscopies, but nine had heart attacks during the following 5 years. All nine were among the quarter of patients with the greatest degree of calcification visible on the CT scans. Had elevated risk been recognized in those patients, doctors could have taken steps to protect them, Davila says.

Not all researchers consider CT scanning of the colon as effective as conventional colonoscopy (SN: 5/1/04, p. 285), but scans provide a "rich source of additional data" that are useful in assessing unrelated health risks, Davila says.--B.H.