Virtual Colonoscopy: A Noninvasive Option for Cancer Screening

This year more than 145,000 new cases of colorectal cancer will be diagnosed in the United States. In a large number of those cases, the cancer will be advanced. That means they’ll be harder to treat. That also means they’ll be more likely to be fatal. The earlier colorectal cancer is found, the easier it is to treat. And that makes a cure more likely. You can even prevent the disease if polyps in the colon and rectum are found and removed before they become cancerous.

A polyp in the colon as seen by virtual colonoscopy.

The best defense against colorectal cancer is regular screening for people ages 50 and older and those at high risk. Unfortunately, many people don’t take advantage of the excellent screening tools available. One reason could be the invasiveness of the methods used. But now there is a tool that makes screening for polyps and colorectal cancer less invasive and less uncomfortable. The tool is virtual colonoscopy.

Colorectal polyp in the sigmoid colon viewed by CT scan (A), virtual colonoscopy (B), and conventional colonoscopy (C).

Less Risk and Discomfort

Virtual colonoscopy is a safe, noninvasive way to find colorectal polyps and other abnormalities. The most thorough screening for colorectal cancer involves a doctor viewing the entire colon. A virtual colonoscopy lets doctors examine the whole colon for polyps and cancers using a CT scanner and virtual reality software. That makes it less invasive than the standard screening methods. Conventional colonoscopy, for instance, requires the use of a long viewing tube that is inserted through the rectum and colon. And barium enemas can be very uncomfortable procedures. If virtual colonoscopy encourages more people to be screened, experts say, it could save thousands of lives.

Colonoscopy, barium enema, and virtual colonoscopy all involve risks. All 3 also involve a certain amount of discomfort. But studies have shown that people experience the least amount of risk and discomfort with virtual colonoscopy. “Risks associated with virtual colonoscopy are minimal compared with the conventional procedure,” says radiologist Matthew Barish, MD, an expert on virtual colonoscopy. “The only discomfort is cramping during bowel inflation, which is usually mild. Unlike conventional colonoscopy, no anesthesia is required and the person can return to normal activities immediately after the procedure. However, if abnormal polyps are found, the doctor must still remove or cauterize them with conventional colonoscopy."

Studies performed at the Center for Virtual Colonoscopy at Boston Medical Center and elsewhere suggest that virtual colonoscopy may be more effective in finding polyps than a barium enema. Virtual colonoscopy is an important component of colon imaging and possible screening, but more study is needed to prove that it is as accurate as standard colonoscopy.

What the Procedure Is Like

If you are screened using virtual colonoscopy, you will go to the radiology department of a hospital or clinic. Before the test, you need to cleanse your bowels. This involves using a laxative your doctor prescribes or going on a 48-hour liquid diet. You might also be given an enema using bisacodyl and sodium phosophate. The bowel preparation causes your stool to turn to liquid and allows the colon to be “cleansed.” During the time your bowels are being cleansed, you will experience frequent and loose stools. So it is important to drink fluids to prevent dehydration.

On the day of the procedure, the doctor places a small, flexible rubber tube in your rectum. Your colon will then be gently filled with air to a level you can tolerate. While you lie on your back and then on your stomach, a radiologist will take a CT scan of your abdomen.

A CT scan creates detailed pictures of the colon on a computer. These pictures allow the radiologist to view polyps or other abnormalities. If there are none, you won’t need other procedures. If the doctor finds polyps or cancers, you will need to have a traditional colonoscopy. The doctor can then remove tissue, called a biopsy, and study it under a microscope.

The test only takes between 10 and 20 minutes. There is no need to be sedated as there is with a standard colonoscopy. So after the procedure, you can return to your normal activities immediately. That means you can even drive yourself home or back to work.

Cecal carcinoma and polyp viewed by CT scan (A), virtual coloscopy (B), and conventional colonoscopy (C).

Discuss Your Options With Your Doctor

Virtual colonoscopy may not be for everyone. Studies are still under way to evaluate its effectiveness compared with other screening methods. And if you are at a higher risk for colorectal cancer, the new procedure will not reduce the likelihood that you will at some point need a traditional colonoscopy. Finally, not all insurance plans cover the new procedure.

But one thing is clear. If you are older than age 50 or are at high risk, it’s important to have regular screenings for colorectal cancer. Talk with your doctor about your options and whether virtual colonoscopy is one to consider.