Colonoscopy allows a doctor to look inside the colon for bleeding, cancer, and polyps. Polyps are small growths that can become cancerous. A colonoscope is a long, slender, flexible, hollow, lighted tube that is roughly the thickness of a finger. The scope, inserted through the rectum and into the colon, is connected to a video camera and a video display. A gentle sedative is given before the procedure, which takes 30 minutes to an hour to perform.
Virtual colonoscopy is a new test that is being considered as a different way to see the colon.
During a CT scan, a person lies still on a table and passes through an X-ray machine that looks like a doughnut. Because the procedure involves X-rays rather than the insertion of the colonoscope, virtual colonoscopy eliminates some of the discomfort of regular colonoscopy, takes half the time, and does not require sedation. However, if abnormalities are seen during virtual colonoscopy, a regular colonoscopy is still needed so that the lesion can be removed and studied to see if it is cancerous. Currently, virtual colonoscopy is still considered experimental as a screening tool for colon cancer. Several studies are under way to examine the usefulness of virtual colonoscopy as a standard screening test for colon cancer.