Colonoscopy Less Effective On Right Side

Armen Hareyan's picture

Colonoscopy appears to reduce the overall risk of death from colorectal cancer, a new study suggests, but it is ineffective at preventing death from cancers that originate in the right side of the colon.

Researchers studied the health records of more than 10,000 people aged 52-90 years who received a colorectal cancer diagnosis between 1996 and 2001 and who had died of the disease prior to 2003 and compared history of colonoscopy to over 50,000 people who had not died of colorectal cancer selected randomly from the Ontario population. The study sheds light on the need to explore the differences in cancer development between the left and right sides of the colon.

“While colonoscopy remains the gold standard for evaluation of the colon, our study sheds light on some of the real-world limitations of this practice for screening and prevention,” says Dr. Nancy Baxter, a colorectal surgeon and researcher at St. Michael’s Hospital and scientist at the Institute for Clinical and Evaluative Sciences (ICES). “At the same time, the findings suggest there may also be opportunities to improve the quality of the test.”


Baxter was the lead author of the study, published today on the Annals of Internal Medicine website and in print in the January 6, 2009 issue.

The Cleveland Clinic reporting on Colonoscopy describes it as an outpatient procedure in which the inside of the large intestine (colon and rectum) is examined. A colonoscopy is commonly used to evaluate gastrointestinal symptoms, such as rectal and intestinal bleeding, abdominal pain, or changes in bowel habits. Colonoscopies are also performed in individuals without symptoms to check for colorectal polyps or cancer. A screening colonoscopy is recommended for anyone 50 years of age and older, and for anyone with parents, siblings or children with a history of colorectal cancer or polyps.

"During a colonoscopy, an experienced physician uses a colonoscope (a long, flexible instrument about 1/2 inch in diameter) to view the lining of the colon. The colonoscope is inserted into the rectum and advanced through the large intestine. If necessary during a colonoscopy, small amounts of tissue can be removed for analysis (a biopsy) and polyps can be identified and entirely removed. In many cases, a colonoscopy allows accurate diagnosis and treatment of colorectal problems without the need for a major operation."

* You are asked to wear a hospital gown and remove eyeglasses.
* You are given a pain reliever and a sedative intravenously (in your vein); you will feel relaxed and somewhat drowsy.
* You will lie on the left side, with your knees drawn up towards your chest.
* A small amount of air is used to expand the colon so the physician can see the colon walls.
* You may feel mild cramping during the procedure; cramping can be reduced by taking slow, deep breaths.
* The colonoscope is slowly withdrawn while the lining of your bowel is carefully examined.
* The procedure lasts from 30 minutes to one hour.