A virtual colonoscopy uses imaging technology known as computerized tomography (CT) to produce hundreds of cross-sectional images of the entire abdomen and its organs. A virtual colonoscopy is used to look for the cause of:

• Abdominal pain, changes in bowel movements or weight loss
• Anemia due to low iron
• Blood in the stool or black tarry stools

A virtual colonoscopy can show irritated and swollen tissue, ulcers and abnormal growths including polyps. In addition, this exam looks at the entire abdomen and can show abnormalities outside of the gastrointestinal (GI) tract. A virtual colonoscopy can also be used to screen for colon cancer.

You will need to empty your colon prior to the exam. Any residue in your colon may obscure the images taken during the exam. Your doctor will provide you with specific instructions to accomplish this. Make sure you tell your doctor about all of the medications you are taking. You may need to stop taking certain medications before your exam.

You will be asked to stop eating solid foods a day or two before the exam. To avoid dehydration, you will need to follow a liquid diet that includes clear, fat-free bouillon or broth, gelatin, strained fruit juice, water, plain and unsweetened coffee or tea, or diet soda. You will not be allowed to eat or drink anything after midnight the night before your exam. You may be asked to take a laxative in either pill or liquid form the night before the exam, and you may also need to use a suppository to clear any remaining residue in your colon.

You may be asked to drink a contrast agent before your exam. This medication helps identify stool in your colon and helps the doctor differentiate between colon abnormalities and stool residue.

You’ll begin the exam lying on your side on the exam table with your knees drawn up towards your chest. The doctor will place a catheter, or a small tube, inside your rectum to fill your colon with air or carbon dioxide. The air or gas, which helps create clear images, may cause a feeling of pressure in your abdomen. Sedation is not necessary for a virtual colonoscopy, but you may be given medicine to reduce the likelihood of stomach cramps during the exam.

For the next part of the exam, you’ll lie on your back, and the exam table will be moved into the CT machine. In order to get accurate, clear images, you will need to remain completely still. You may be asked to turn and hold various positions, and you may be asked to hold your breath at times. If necessary, a contrast agent may be given through an IV in your arm to help create clearer images.

The computer combines all the images, which are viewed on a video monitor. The images can be viewed as two-dimensional CT scans, which display any possible abnormalities protruding from the lining of the colon. The images can also be combined to generate a three-dimensional view of the colon, allowing doctors to “fly through” the organ looking for any suspicious growths or protrusions.