Virtual colonography or computed tomography colonography is a noninvasive procedure that uses computed tomography scanning to determine the presence of colon polyps.

Colon polyps have been shown to be the precursor lesions for most colon cancers. Identification and removal of colon polyps before they become cancerous is the purpose of colon screening. The VCU Department of Radiology was among the first in Virginia to test and use more patient-friendly methods of screening for colon polyps. 

Virtual colonography (VC) makes it possible to evaluate the entire colon, without risk of bowel perforation, or complications from sedation associated with standard colonography. VC is accurate in identifying significant polyps and is attractive to patients who are simply not willing to undergo the more invasive traditional colonography.

Early studies show that VC is comparable to conventional colonography in terms of identifying polyps six millimeters or greater in size. The VCU Department of Radiology use VC as a diagnostic tool to confirm or rule out the possibility of cancer. If large polyps are identified, traditional colonoscopy is required for biopsy and removal.

The VC procedure itself calls for the patient to lie on the computed tomography (CT) scan table while the colon is partially inflated using a tiny air tube. Two 5-second CT scans are performed, one with the patient on his or her back and the other with the patient lying on his or her stomach.

VC relies on specially developed computer software to recreate the inside of the patient’s colon using two-dimensional and three-dimensional images. The process allows a “fly-through” or “virtual” evaluation of the colon that provides the precise location and size of colon polyps.