Virtual colonoscopy does not allow therapeutic maneuvers such as polyp and tumour removal or biopsy, nor visualization of lesions smaller than five millimeters; if a growth or polyp is detected using CT colonography, it would require removal during a standard colonoscopy. Surgeons have used the term pouchoscopy to refer to a colonoscopy of the ileo-anal pouch. Medical uses
Conditions that call for colonoscopies include gastrointestinal hemorrhage, unexplained changes in bowel habit and suspicion of malignancy. Colonoscopies are often used to diagnose colon polyp and 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 that calls for a colonoscopy, usually along with an esophagogastroduodenoscopy (EGD), 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 diverticulosis, inflammatory bowel disease (Crohns disease, ulcerative colitis), colon cancer, or polyps. Colonic polypectomy has become a routine part of colonoscopy, allowing quick and simple removal of polyps during the procedure, without invasive surgery. Colon cancer screening
Colonoscopy is one of the colorectal cancer screening tests available to people in the US who are 45 years of age and older.
Based on public-domain NIH Publication No. 02-4331, dated February 2002. Patient Education Brochures. American Society for Gastrointestinal Endoscopy information
Colorectal Cancer Incidence and Screening — United States, 2008 and 2010 Centers for Disease Control and Prevention