CT Colonography (CTC) is an advanced type of x-ray exam that uses computed tomography (CT) scanning to obtain an interior view of the colon (the large intestine) that can ordinarily only be seen with an endoscope inserted into the rectum. This new minimally invasive test provides three-dimensional images that can depict many polyps and other lesions as clearly as when they are directly seen by colonoscopy.
The major reason for performing CT Colonography is to look for polyps in the colon (large intestine). Polyps are benign growths that arise from the inner lining of the intestine. Some polyps may grow and turn into cancers. The aim is to detect these growths in their early stages, so that they can be removed before cancer has had a chance to develop.
It is very important to clean out your bowel the night before your CT Colonography examination so that the radiologist can clearly see any polyps that might be present. On the day before the procedure you will likely be asked not to eat, and to drink only clear liquids like water, black tea & coffee, cola and to avoid dairy products. After midnight, you should not eat or drink anything. You will be given 2 sachets of laxative (usually picolax) to be taken the day before the procedure. Just follow the detailed instructions from radiology. You can take your usual prescribed oral medications with limited amounts of water.
You may be asked to remove some or all of your clothes and to wear a gown during the exam. You may also be asked to remove jewelry, eye glasses and any metal objects or clothing that might interfere with the x-ray images.
If you do take insulin or tablets you need to make sure you have enough to eat on the day before your appointment to prevent low blood sugars and you should follow the advice given by the Radiology Department (usually in a special accompanying leaflet).
Women should always inform the doctor or radiographer if there is any possibility that you could be pregnant. Many imaging tests are not performed during pregnancy because radiation can be harmful to the fetus.
Following bowel cleansing the evening before, you will lie down on your stomach or on your side on the scanner table. 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. In either case, you will be able to control the amount of air or gas passing into the colon. The purpose of the gas is to distend the colon a little to eliminate any folds or wrinkles that might obscure any polyps that are there. As the table moves through the scanner, you will be asked to hold your breath for about 15 seconds. A second pass is made through the scanner after you have turned onto your back, to make sure that all sections of the colon are air-filled. 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 and you are free to leave.
The vast majority of patients who have CT Colonography report a feeling of fullness during the exam, as if they need to pass gas, when the colon is inflated. Significant pain is uncommon, however, occurring in fewer than 5 percent of patients. A muscle-relaxing drug is usually injected intravenously to lessen discomfort. After the tube is inserted, your privacy will be respected. The scanning procedure itself causes no pain or other symptoms. You will be alone in the examining room during CT, but a radiographer will be in the adjacent control room and is able to see and hear you, and can speak to you at any time. The entire examination can be completed within 30 minutes.
A radiologist, a physician specifically trained to supervise and interpret radiology examinations, will analyze the images and send a signed report to your primary care or referring doctor, who will share the results with you.
If you have a query about having the CT, please ring the Radiology Department between 9am and 5pm, Monday to Friday & 9am and 12pm Saturday.