Colonoscopies could miss dangerous lesions: report

WASHINGTON (Reuters) - The most dangerous types of pre-cancerous lesions in the colon could be missed by colonoscopies, researchers cautioned on Wednesday.

More than 9 percent of the growths that could become tumors are flat and difficult to see, the team at the Veterans Affairs Palo Alto Health Care System in California found.

Colonoscopies are examinations of the colon that use an endoscope -- a little camera on a flexible tube. The doctor doing the examination can see and remove polyps, the small growths that can become tumors.

But not every pre-cancerous lesion stands up. There is a type called a flat, non-polypoid colorectal neoplasm and the California team found they are both more common and more dangerous than previously thought.

Dr. Roy Soetikno and colleagues examined the results of 1,819 colonoscopies among patients at their hospital.

They found 170 of these flat lesions, or 9.35 percent of all growths detected.

Once removed, they were 10 times as likely as the more obvious growths to contain cancerous tissue, Soetikno's team reported in the Journal of the American Medical Association.

They noted that up to 1 percent of patients who have colonoscopies develop cancer within three years afterward. These missed flat lesions may explain some of these cases, they said.

Dr. David Lieberman of the Portland VA Medical Center in Oregon agreed. "There has been increasing recognition that colonoscopy, even by experienced and well-trained endoscopists, may fail to detect important colon pathology," Lieberman wrote in a commentary.