Colonoscopy Has a 'Right Side' Blind Spot

Colonoscopy does a good job of detecting early signs of disease on the left side of the colon, or large intestine, but is not as effective at spotting potential problems of the right side of the organ. This means a colonoscopy's success at preventing colorectal cancer deaths seems to lie with its ability to uncover so-called "left-sided" problems.

"We did find that colonoscopies are effective -- that's the good news. It's still one of the best screening tests for any cancer that we have," said study author Dr. Nancy Baxter, a colorectal surgeon with St. Michael's Hospital in Toronto.

"But it's not perfect," she added. "And it does not appear to be as effective in picking up growths on the right side of the colon as it is in detecting them on the left side."

The findings are published online Dec. 16 in the Annals of Internal Medicine.

In an accompanying editorial in the journal, Dr. David F. Ransohoff, a professor of cancer epidemiology at the University of North Carolina, suggested that the mortality risk reduction offered by colonoscopies is probably closer to 60 percent to 70 percent, rather than the 90 percent figure typically cited.

Dr. Judith Collins, section chief of gastroenterology at the VA Medical Center in Portland, Ore., said that despite the apparent limitations highlighted in the new study, colonoscopies are still the gold standard for detection of colorectal cancer.

"This is a totally preventable cancer," she said. "So whether screening for it results in a 60 percent reduction in death or 90 percent reduction, there's just no other cancer that we can see this well, and colonoscopy certainly reduces mortality. And that's the bottom line. There are a lot of variables that show that it is not a perfect test, but it's still a very good test."

Bonnie - I would be interested to see if the virtual colonoscopy fares better in picking up the right side.