CT Colonography is a novel method to evaluate the colon. It involves thin section imaging through the abdomen after distension of the colon with air. It has been shown to be sensitive in detecting colonic polyps as small as 1 cm, and may also detect smaller polyps, though with a lower sensitivity. It has been accepted in the medical community, mainly to be used in patients unable to undergo conventional colonoscopy, or in patients who have had an incomplete colonoscopy.
The exam requires you to prepare your colon as for routine colonoscopy. This entails fasting, except for fluids, for the day before the exam. In the CT room, a rectal tube is inserted and air is insufflated in order to distend your colon (in order to see the wall of the colon, it is important for it to be distended). This is no different than during normal colonoscopy.
After distension, a CT scan is performed, which is quite brief, and this is where CT colonoscopy is much more easily tolerated than routine colonoscopy, which can take quite a long time.
After the CT is performed, the images are processed on a computer workstation, and a report is usually sent to your doctor within 24 hours.