Because of the strong link between genetics and colon cancer, it is important for people to know if any of their relatives have had colon cancer or polyps and if so, when the disease first appeared. This makes it possible to determine whether a person is at increased hereditary risk, and thus requires more frequent screening.
Several tests are used to screen for colon cancer. The fecal occult blood test detects hidden blood in the stool, a sign of colon cancer, and is simple and inexpensive. Flexible sigmoidoscopy, in which a lighted tube (endoscope) is inserted into the rectum to the end of the sigmoid colon, allows a gastroenterologist to examine the lining of the colon, sample tissue for examination in the lab (a biopsy) and remove polyps if necessary.
Colonoscopy is a similar test in which the entire colon is examined. This test is performed while the patient is sedated. Screening for people with no known risk factors for colon cancer should begin after age 50, and should include an annual fecal occult blood test and a flexible sigmoidoscopy every three to five years. People with strong risk factors, such as those who have ulcerative colitis, need to be screened more frequently beginning at a younger age.
Another diagnostic test sometimes used in screening is a barium enema X-ray, in which a contrast agent, barium, is inserted into the body through the rectum, making it possible for a radiologist to examine the shape of the colon and look for abnormalities.
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