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Virtual Colonoscopy: The Latest Colon Cancer Screening Tool

Here is a view of a polyp in the colon using computer enhanced detection during virtual colonoscopy, also called CT colonography.

Consider it a rite of passage when you reach 50. At this age, the American Cancer Society recommends that men and women undergo colon cancer screening. Traditional screening options include fecal occult blood testing, barium enema, sigmoidoscopy and colonoscopy. "Today there is a newer 'virtual colonoscopy,' or CT colonography, examination that shows great promise as a screening tool," says David Vining, M.D., professor of diagnostic radiology and nuclear medicine at the University of Maryland School of Medicine.

In the United States, colon cancer is the second leading cause of cancer deaths. "No one should die from this disease. Most colon cancers arise from pre-cancerous polyps, so if we screen and detect polyps, physicians can remove them and potentially prevent or cure colon cancer before it ever becomes a problem," says Jean-Pierre Raufman, M.D., professor of medicine at the University of Maryland School of Medicine and head of the Division of Gastroenterology at the University of Maryland Medical Center.

At the University of Maryland, colon cancer screening uses a team approach between gastroenterology, radiology and surgery. While fecal occult blood testing, barium enema and sigmoidoscopy are beneficial as screening tools, they are also somewhat controversial due to their suboptimal results. A better procedure that works as a screening and diagnostic tool is colonoscopy. Gastroenterologists use a scope and camera to investigate the colon for polyps or other signs of cancer. If a polyp is detected, it can often be removed at that time with the scope.

The newest screening tool, CT colonography -- which was invented by University of Maryland radiologist Dr. Vining in 1993 and is being offered at the University Maryland Medical Center -- is considered a viable option for men and women over the age of 50 without colon cancer symptoms or a family history of polyps. Unlike colonoscopy, the CT colonography cannot be used to remove a polyp.

"Some physicians are quick to criticize virtual colonoscopy, saying that if the test is positive, then a patient will need further evaluation with conventional colonoscopy, and should have done that in the first place," says Dr. Vining. He counters this argument by pointing out that only 20% of the unsuspecting screening population has a polyp, so if everyone in this population undergoes colonoscopy, eight out of 10 people could have had the virtual colonoscopy alone.

"Virtual colonoscopy is performed using an advanced multidetector spiral CT scanner to generate 2-D and 3-D images of the colon, as well as images of other organs in the abdomen and pelvis," explains Barry Daly, M.D., professor of diagnostic radiology at University of Maryland School of Medicine and director of abdominal imaging at the University of Maryland Medical Center. An added advantage of this procedure is that it may detect unsuspected diseases and conditions outside of the colon, something that is not possible with traditional colon cancer screening methods.

Right now, the CT colonography screening is not covered by insurance. However, as a diagnostic procedure it may be covered. A patient undergoing virtual colonoscopy is required to take laxatives to cleanse the bowel, and during the procedure the colon is inflated with gas. Unlike conventional colonoscopy, the virtual procedure does not require sedation and takes just minutes to complete the scan.

No matter what screening option a patient chooses, the University of Maryland team strongly recommends that people age 50 and older undergo some form of colon cancer screening. Colon cancer is preventable and easily treatable in its early stages.

This page was last updated on: August 1, 2008.

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