Virtual Colonoscopy

Virtual colonoscopy, also known as CT colonography, at UW Health is a safe and less invasive exam used for colon polyp screening.




For information or questions regarding Virtual Colonoscopy, please call the Virtual Colonoscopy Office at (608) 263-9630 to speak with the department assistant or nurses.


Overview of Virtual Colonoscopy


A computed tomography (CT) scan makes a picture of the inside of the colon which allows the doctor to see the entire colon lining without needing to insert a scope.


The CT scan images also allow the doctor, who is a radiologist specially trained in virtual colonoscopy, to take a limited look outside the colon for problems in the abdomen and pelvis. However, the main purpose of the virtual colonoscopy exam is to screen for polyps (growths) in the large intestine (colon and rectum).


If a large polyp is found in the colon, an optical colonoscopy may be needed to remove it. "Large" polyps are those 1 cm (about 3/8 inch or the size of a garden pea) or greater and should be removed because they have a higher chance of becoming cancer. A growth of this size is found in less than 5 percent of all patients. A nurse will arrange for the optical colonoscopy the same day, if needed.


"Small" polyps, those between 6 mm and 9 mm (about 1/3-1/4 inch), are found in the colon 7-8 percent of the time. Polyps of this size have a less than 1 percent chance of becoming cancer. Doctors at UW Health can safely watch a small colon polyp over time by having a follow up virtual colonoscopy exam in 3 years. But small polyps can also be removed by optical colonoscopy on the same day or later. Patients are given both options to choose from if a polyp of this size is found.


Patients who take blood thinners such as Coumadin® or Plavix® can safely have a virtual colonoscopy exam without stopping these medicines. In the small number of cases that a polyp is found which needs to be removed, the optical colonoscopy would be set up by their doctor at a later date.


Preparing for Virtual Colonoscopy


Virtual Colonoscopy Preparation Kit


The virtual colonoscopy preparation kit contains all of the medicines needed to prepare for the exam and written instructions. The kit is paid for by the UW Radiology Department and can be picked up at any UW Health Pharmacy once the virtual colonoscopy exam has been scheduled. If you live out of the area or cannot go to the pharmacy to pick it up, we can have the kit mailed to you.


The day before the virtual colonoscopy exam, a clear liquid diet is followed. You must also clean your colon with laxatives and take a small amount of contrast medicines for the CT images. Most people take a low-volume preparation that can be started at home after work. On the preparation day, you can drink clear liquids until midnight. After midnight, you should have nothing to eat or drink except sips of water with medicines.


Virtual Colonoscopy Procedure


No IV, pain or sedation medicine is needed for this exam so you can drive yourself to and from the exam. The exam is performed by a CT technician and most often takes 15 minutes or less to do. While lying on the CT exam table, a small tube is gently placed 2-3 inches into the rectum (this feels like a digital rectal exam). Carbon dioxide is placed slowly into the colon. The exam should not be painful, though the carbon dioxide can cause some abdominal fullness, discomfort, or cramping. These feelings should go away when the exam is over. Images are taken while lying on your back and then on your stomach. You hold your breath for about 10 seconds while the CT scanner is working.


After the Virtual Colonoscopy


After the virtual colonoscopy exam, you can return to your normal routine right away. You may drive or go to work if you choose. If you want to have the option to have an optical colonoscopy if a polyp is found, then do not eat or drink anything. The virtual colonoscopy office will call you with the colon polyp results within 2 hours. If no colon polyps are found, you can eat, drink, and resume your routine.


If a small or large polyp is found, a nurse will review your options for follow-up. If the polyp is 1 cm or greater, an optical colonoscopy can be arranged that same day so that a second prep is not required. If the polyp is between 6 mm and 9 mm, options of optical colonoscopy for polyp removal or watching the polyp with virtual colonoscopy in 3 years are reviewed with you. The nurse will help set up whichever option you feel most comfortable with and answer any questions.


Virtual colonoscopy also allows the doctor to take a limited look outside the colon for problems in the abdomen and pelvis. Some examples of extra findings that may be seen include abdominal aortic aneurysm and masses or cancers involving other abdominal organs. If any concerning findings are seen outside the colon, the results will be given to your referring doctor and written in the virtual colonoscopy report.