CT scan no match for colonoscopy

Colonoscopy is better at detecting potentially dangerous colon polyps than computed tomography (CT) scanning is, a new study reveals. The conclusion differs from that of a recent report that found the two procedures to be equally effective (SN: 12/06/03, p. 355: No Scope: CT scan works as well as colonoscopy).

In colonoscopy, a physician inserts a flexible tube equipped with a tiny camera and snipping device into a patient’s colon via the rectum. The doctor uses the device to spot and remove polyps—a procedure that wipes out practically all budding colon cancers. In a CT scan, a radiologist uses X-ray images taken from outside the abdomen to spot polyps. If the scan reveals polyps that should be removed, the patient then undergoes a colonoscopy.

In the new study, 600 people of an average age of 61 agreed to undergo a CT scan of the colon followed by a colonoscopy. The colonoscopies found and removed polyps at least 6 millimeters in length in 103 people, whereas the CT scans detected such growths in only 41, the researchers report in the April 14 Journal of the American Medical Association.

The findings suggest that CT scanning isn’t yet reliable enough for replacing colonoscopy for polyp detection, says study coauthor Peter B. Cotton, a gastroenterologist at the Medical University of South Carolina in Charleston.

It remains unclear whether CT scans lack enough detail to spot some polyps or if doctors simply have too little experience with the technique to detect small growths, Cotton says. Colonoscopy has been in use much longer than CT colon scans.

Colonoscopy has made most colon cancers preventable, but the procedure requires some sedation if the individual is to avoid pain and discomfort. Fewer than half of people in the United States over age 50 have had a colonoscopy.