Virtual Colonoscopy

Frequently Asked Questions

Advanced Diagnostic Radiology currently provides Virtual Colonoscopy, a new screening test for polyps and colorectal cancer that may improve the odds of early colorectal cancer and polyp detection by make screening examinations more acceptable to patients and more affordable.

What is Virtual Colonoscopy?

Virtual Colonoscopy (VC), which is also known as CT colonography, is the newest screening test for colorectal cancer. High-quality Virtual Colonoscopy is presently available at only a few centers in the country. This test uses a helical CT (computed axial tomography) scanner to take images of the large intestine (colon and rectum). Special computers and software convert this two-dimensional information into a three-dimensional image of the large intestine that a radiologist can scan for abnormal growths.

What is a CT (Computed Tomography) Scanner?

A CT scanner is a special x-ray machine combined with a computer that produces cross-sectional images or "slices" of any part of your body. Unlike a standard "flat" x-ray image where some body structures overlap others, a CT scan shows structures within each slice on a three-dimensional plane. As a result, the doctor who views a CT scan can see your entire anatomy.

The CT scan machine is open around you, does not touch you and is not confining. It should not be confused with an MRI scanner that is more of a tunnel-type structure. Even patients who suffer with claustrophobia find CT scans to be relatively fast and easy.

How is Virtual Colonoscopy Different from Traditional Colonoscopy?

With traditional colonoscopy, a slender, flexible tube about the thickness of a finger is inserted into the rectum and is advanced thorough the entire colon. The tube is connected to a video camera and light source so the physician can examine the inside of the colon. The patient is given a sedative before the procedure to reduce worry and discomfort. Afterwards, the patient must wait for the sedative to wear off. Another driver must accompany the patient to provide safe transportation home. The patient usually misses a day of work. Total time required in the endoscopy suite is 1 1/2 to 2 hours.

With Virtual Colonoscopy, a small tube is inserted into the rectum, and the colon is filled with air or carbon dioxide to make it easier to view. The patient may feel mild abdominal cramping and fullness, but most find the procedure more comfortable than a traditional colonoscopy. No sedative is required, so the patient can go home or back to work immediately after the procedure. There is no requirement to come with a driver. Total time required in the CT area is about 30-45 minutes.

What Should I Expect?

You will be registered at the Advanced Diagnostic Radiology Reception Desk and will be directed to the CT Waiting area. You will be taken from there to a dressing room and asked to put on a patient gown. From there, you will be taken to the CT scanner room and placed on a table. You will have an enema tip inserted into your rectum and your colon will then be filled with air or carbon dioxide which will enable your colon to be seen in the CT images.

A Virtual Colonoscopy test takes about 15 minutes of the patient’s time in the CT scanner room. During that time, you will be asked to lie very still on a table that moves in and out of a round opening called a "gantry". The ring inside the gantry contains an x-ray tube mounted on one side and receptors mounted on the opposite side. As the x-ray tube moves around you, the receptors on the opposite side measure the amount of x-ray that passes through you. These measurements are fed into a computer that processes the information and produces images on a video screen for a radiologist to view.

What Preparation is Required?

Excellent bowel preparation is critical for obtaining excellent diagnostic test results. The preparation for a Virtual Colonoscopy begins 2 days before the examination. The bowel preparation involves taking a liquid diet for one day, using laxatives to remove all stool (feces) from the colon, and swallowing contrast agents to tag any remaining stool or liquid so that it can be electronically removed by the computer.

All of the required preparation materials and instructions will be available at the Advanced Diagnostic Radiology Reception Desk for you to pick up. After your exam is scheduled, you need to pick up your prep materials and instructions at least 3 days before your study. These are provided at no cost. Should you need the prep kit mailed to you, please call Advanced Diagnostic Radiology at 301-777-3522 or toll free at 1-866-816-2313. Be sure to allow at least 1-2 weeks for mailing.

How Accurate is VC?

New scientific reports indicate that the accuracy of Virtual Colonoscopy is comparable to traditional colonoscopy when performed with multiple-detector CT scanners, computer equipment and software like those used at Advanced Diagnostic Radiology. A recent article in the New England Journal of Medicine reported that the two tests were equally sensitive for detecting growths that were 6 mm or greater in size. At this size, a cancerous or precancerous growth is considered highly treatable. If Virtual Colonoscopy detects a significant polyp, traditional colonoscopy will be required for further investigation and polyp removal. However, traditional colonoscopy is necessary in fewer than 1/3 of patients that undergo Virtual Colonoscopy.

As currently performed at Advanced Diagnostic Radiology, Virtual Colonoscopy should also be as accurate for ruling out (excluding) cancer and significant polyps as traditional colonoscopy. This is most important because most adults don’t have significant polyps.

VC has not been studied for use in evaluating inflammatory bowel diseases such as Crohn’s disease or ulcerative colitis.

Are There Any Risks?

The risks with VC are minor. They include radiation exposure, which is less than with a traditional barium enema. Bowel injury could theoretically occur, although no cases have been reported to date. This risk should be much lower than with traditional colonoscopy.