The disadvantages of virtual colonoscopy include the danger of missing small polyps, the inability to biopsy or remove polyps or other growths, the radiation used to make X-ray images and the dangers of colon inflation. Also, medical insurance doesn't always cover the virtual method, notes Johns Hopkins Medicine.
Virtual colonoscopy attempts to accomplish the same goal as conventional colonoscopy: to get a view of any polyps or other growths inside the colon. Polyps growing in that area can become colon cancer, which is why the American Cancer Society recommends that people start receiving colon cancer screenings at the age of 50 -- or even younger for people with a family history of colon cancer or other elevated risk factors, as stated by Johns Hopkins Medicine.
A computer takes hundreds of cross-sectional X-rays of the patient's colon to build the virtual colonoscopy before assembling those images into an image that doctors and radiologists analyze. This process causes less discomfort than conventional colonoscopy and takes less time. There is also less risk of perforating the bowel. However, the procedure involves inflating the colon in order to take the X-ray pictures, which involves a risk of perforation, and polyps smaller than 10 millimeters may not make it into the images, whereas in conventional colonoscopy the procedure could find polyps of that size, as stated by Johns Hopkins Medicine.