Radiology – CT Colonography

CT colonography, also called virtual colonoscopy, creates images of the inside of the colon and rectum. It uses CT (computed tomography) technology to do this, and it is less invasive than an actual colonoscopy.

CT Colonography

Our skilled team of technologists provides high-quality imaging and compassionate care for each patient. These tests are read by our board-certified, subspecialty-trained radiologists who interpret images of specific body areas and systems for both adults and children.

In most cases, CT colonography is done to screen for polyps or cancers in the large intestine. Polyps are growths that begin in the lining of the intestine. A very small number of them may grow and turn into cancers.

CT colonography can find problems but not treat them. If any polyps are found that need to be removed, that will be done during a colonoscopy.

Penn State Health takes part in the Image Gently program to reduce radiation exposure for our patients. Our advanced imaging equipment can adjust radiation exposure for each image. This lets us take the best quality images with the least possible radiation.


You will begin your prep 24 hours prior to your exam. Start by picking up a prep-test kit from our Radiology Department. This kit includes glass bottles so we are unable to send them through the mail. Detailed instructions are included.

IV contrast is necessary for some CT exams. Please let your doctor know if you have had a past reaction to X-ray contrast dye.


A very small, flexible tube will be passed two inches into your rectum. This allows air to be gently pumped into the colon using a hand-held squeeze bulb. In some cases an electronic pump is used to deliver carbon dioxide gas into the colon. The purpose of the gas is to distend the colon as much as possible. This eliminates any folds or wrinkles that might hide polyps.

Next, the table will move through the scanner. You will be asked to hold your breath for about 15 seconds or less during this time. Then you will turn over and lie on your back or side for a second pass through the scanner. The entire test usually takes about 15 minutes.

Most people who have CT colonography report a feeling of fullness when the colon is inflated during the exam, as if they need to pass gas.


The radiologist will analyze the images and send a report to your doctor. This usually happens within 48 hours. Your doctor will then discuss the results with you.