Colon and Rectal Cancers - Dietary Factors

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Guidelines for Increased-Risk Groups. Screening, particularly with colonoscopy, in increased- and high-risk populations can save lives. The most important risk factors that may prompt screening before age 50 or more frequent screenings are:

• A known family history of inherited colorectal cancer syndromes such as familial adenomatous polyposis (FAP) or hereditary nonpolyposis colorectal cancer (HNPCC)
• A strong family history of colorectal cancer or polyps, especially in first-degree relatives (parent, sibling, or child) who developed these conditions younger than age 60
• A personal history of colorectal cancer or polyps
• A personal history of chronic inflammatory bowel disease. [For specific screening recommendations for patients with inflammatory bowel disease, see In-Depth Reports #103: Crohn's disease and #69: Ulcerative colitis.]

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Patients in these high-risk groups who have changes that are identified as precancerous during colonoscopy will likely have their doctors discuss with them the possibility of a prophylactic or preventive colectomy (removal of the colon).

Description of Screening Tests

Colonoscopy. Colonoscopy allows a doctor to view the entire length of the large intestine using a colonoscope, which is inserted into the rectum and snaked through the intestine. A colonoscope is a long, flexible tube that has a video camera one end. The doctor views images from the colonoscope on a display monitor. The test takes about 30 minutes to perform. If polyps are found, the doctor will remove them. The patient is given a sedative prior to the test, which produces a comfortable “twilight” sleep.

In order for the doctor to perform a successful colonoscopy, the colon and rectum must be completely empty. Your doctor will give you complete instructions for how to prepare during the days preceding the tests, and specific foods and liquids to avoid eating and drinking. The day before the test you will be given laxative solution to clean out the colon. Many people find this cleansing more unpleasant than the colonoscopy itself.