CT colonography uses CT scanning to obtain an interior view of the colon (the large intestine) that is otherwise only seen with a more invasive procedure where an endoscope is inserted into the rectum.
The major reason for performing CT colonography is to screen for polyps and other lesions in the large intestine. Polyps are growths that arise from the inner lining of the intestine. Some polyps may grow and turn into cancers.
The goal of screening with colonography is to find these growths in their early stages, so that they can be removed before cancer has had a chance to develop. Most physicians agree that everyone older than 50 years should be screened for polyps every seven to 10 years. Individuals at increased risk should be screened every five years and may start screening at age 40 or younger. Risk factors for the disease include a history of polyps, a family history of colon cancer, or the presence of blood in the stool.