Colonoscopy is the minimally invasive endoscopic examination of the large colon and the distal part of the small bowel with a fiber optic camera on a flexible tube passed through the anus. It may provide a visual diagnosis (e.g. ulceration, polyps) and grants the opportunity for biopsy of suspected lesions.
Virtual colonoscopy, which uses 3D imagery reconstructed from computed tomography (CAT) scans, is also possible, as a totally non-invasive medical test, although it is not standard and still under investigation. Furthermore, this imaging technique does not allow for therapeutic maneuvers such as polyp removal or biopsy. If a growth or polyp is detected using CT colonography, a standard colonoscopy would still need to be performed. Colonoscopy is similar but not the same as sigmoidoscopy. The difference between colonoscopy and sigmoidoscopy is related to which parts of the colon each can examine. Sigmoidoscopy allows doctors to view only the final 60 cm of the colon, while colonoscopy allows a complete examination of the colon, which can measure well over six feet (two metres) in overall length.
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Intervention: Colonoscopy
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Uses
Indications for colonoscopy include gastrointestinal hemorrhage, unexplained changes in bowel habit or suspicion of malignancy. Colonoscopies are often used to diagnose colon cancer, but are also frequently used to diagnose inflammatory bowel disease. In older patients (sometimes even younger ones) an unexplained drop in hematocrit (one sign of anemia) is an indication to do a colonoscopy, usually along with an EGD (gastroscopy), even if no obvious blood has been seen in the stool (feces).
Fecal occult blood is a quick test which can be done to test for microscopic traces of blood in the stool. A positive test is almost always an indication to do a colonoscopy. In most cases the positive result is just due to hemorrhoids; however it can also be due to polyps (which are easily removed during the colonoscopy procedure), diverticulosis, inflammatory bowel disease (Crohn's disease, ulcerative colitis), or colon cancer.
Due to the high mortality associated with colon cancer and the high effectivity and low risks associated with colonoscopy, it is now also becoming a routine screening test for people 50 years of age or older. Subsequent rescreenings are then scheduled based on the initial results found, with a five- or ten-year recall being common for colonoscopies that produce normal results.
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