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What is Virtual Colonography?

  In March 2008, the American Cancer Society named CT Colonography (virtual colonography) as a front-line screening exam for colorectal cancer. CT Colonography employs cutting-edge, virtual-reality technology to produce three-dimensional "fly-through" images that permit a thorough and minimally invasive evaluation of the entire colorectal structure. 

What are the advantages and disadvantages of CT Colonography?


  • No sedation is required, allowing patients to resume normal activity immediately. 
  • Depicts many polyps and lesions as clearly as when they are seen by optical colonoscopy. 
  • A lower risk of perforating the colon. 
  • Less invasive than optical colonoscopy. 
  • An excellent alternative for patients who have clinical factors that increase risk from colonoscopy, such as treatment with blood thinner or a sever breathing problem. 
  • Can be helpful if the bowel is narrow or obstructed for any reason. 
  • May show abnormalities outside of the colon. 


  • Strictly a diagnostic procedure, biopsies cannot be performed at Dakota Radiology. If there are any significant polyps found, they will have to be removed through conventional colonoscopy. 
  • Although it's a less expensive procedure than conventional colonoscopy, CT Colonography is currently not yet covered by Medicare. Check with your insurance provider about coverage of this exam. 

How should I prepare for this procedure?

The preparation of this exam is similar to the optical colonoscopy beginning with a low-fiber diet 2 days before, a clear liquid diet the day before and the use of a cleansing Kit.  The documents below outline the preparation in detail.

Preparation Instructions
Low Fiber Diet 

What can I expect during this procedure?

Once positioned on the CT table, a very small, flexible tube is passed two inches into the rectum to allow air to be gently pumped into the colon using a hand-held squeeze pump.  The patient will control the amount of air that is passed into the colon.  The purpose of this gas is to distend the colon a little to eliminate any folds or wrinkles that might obscure polyps from the Radiologist's view. The patient will pass through the scanner twice, once facing upwards and once facing downwards. 

Once the scan is complete, the images are sent to a computer system that reconstructs the images into a three-dimensional view for the radiologist to navigate and examine.