CT colonography, also known as virtual colonoscopy is performed by SMIL 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 and passed through the entire colon.
During the CT colonography the technologist will begin by positioning you on the CT examination table, usually lying flat on your back or less commonly, on your side or on your stomach.
A very small, flexible tube will be passed two inches into your rectum to allow air to be gently pumped into the colon using a hand-held squeeze bulb. Sometimes an electronic pump is used to deliver carbon dioxide gas into the colon. Sometimes a retention balloon is inflated on the rectal tube to help keep the tube positioned correctly. The purpose of the gas is to distend the colon as much as possible to eliminate any folds or wrinkles that might obscure polyps from the physician's view.
Next, the table will move through the scanner. You will be asked to hold your breath for about 15 seconds before turning over and lying on their back or side for a second pass that is made through the scanner. In some centers the sequence of positions may be the opposite: facing upward first and then facing down. Once the scan is done, the tube is removed.
The entire examination is usually completed within 15 minutes.
Learn how to prepare for the scan in the CT colonography preparations section.
Find out if this procedure is right for you in the benefits and risks of CT colonography section.
For a downloadable/printable PDF about this exam with preparation instructions click here.