1. Fecal occult blood testing (FOBT) is a test that looks for trace amounts of blood in the patient’s stool that might indicate and early colorectal cancer. Patients with positive FOBT tests are referred for colonoscopy to look for a bleeding source. FOBT testing reduces cancer related death, presumably by detecting cancer at an early stage. FOBT generally does not enable the detection of polyps, as polyps rarely bleed. FOBT is currently indicated in Ontario for patients over the age of 50 and the test is generally repeated on a yearly basis.
2. X-rays such as Barium Enema and CT Colonoscopy (virtual colonoscopy) can be used to detect polyps and cancers. Neither imaging technique is as good as colonoscopy for detecting polyps. If polyps are detected, colonoscopy is required to remove them. No sedation is given for these procedures. Both procedures require a preparation to cleanse the colon.
3. Sigmoidoscopy is a similar endoscopic procedure to colonoscopy but only the rectum and sigmoid colon portion or the last, perhaps one-third of the colon, is examined. This procedure is sometimes chosen because it is easier to perform. Sometimes family doctors perform these in their offices and the procedure can be performed without a complete preparation and without sedation. Polyps that are detected are generally removed at the time of the completion colonoscopy. The disadvantage of a sigmoidoscopy is that the entire colon is not examined and a fair proportion of cancers and polyps develop in the area of the colon that is not seen at the time of sigmoidoscopy.
4. Capsule endoscopy is an amazing new technology to visualize the gastrointestinal tract. It has proven most effective in examining areas of small bowel inaccessible to standard endoscopes. Technology remains limited. It is not proven to be a useful strategy for screening for colorectal cancer.