Virtual Colonoscopy

What Happens During a Virtual Colonoscopy?

Many patients who don’t want to have a colonoscopy opt for virtual colonoscopy, a relatively new medical procedure that scans for adenomatous polyps (pre-cancerous polyps) with a CT machine—although it is not widely available yet in many areas. Virtual colonoscopies do not take a long time to complete and do not require sedation. The test is performed in hospitals, doctors’ offices and radiology centers that have access to medical imaging technology.

The only part of a virtual colonoscopy that might be uncomfortable for the patient is getting the colon inflated with air before entering the CT machine for scanning. Naturally, the gastrointestinal tract (GI tract) has many twists and turns which might obstruct the clarity of the final CT scan and botch results. In order get the best diagnosis, the attending endoscopist (whoever is performing the virtual colonoscopy) will insert a little tube through the patient’s rectum and use a machine attached to the tube to pump air into the colon, basically inflating it and opening the area up for better visibility. Getting air pumped through the colon isn’t necessarily painful, but the patient may feel slight soreness in the abdomen while the machine is on.

Once the colon is prepped and ready to be scanned, the table on which the patient is situated will move through a cylindrical machine called that takes cross-sectional images of the body and puts them together for a final, 3D image. The patient must remain completely still while the CT machine is working; sometimes the endoscopist will ask the patient to hold his or her breath while the pictures are being taken. The scanning process is performed twice—once while the patient is on his or her back and then once again with the patient flipped over.

Is a Virtual Colonoscopy Better than a Regular Colonoscopy?

Unfortunately, virtual colonoscopy is only a limited method of screening for colon cancer. The CT machine will not be able to detect polyps or tumors that are fewer than 5 millimeters in diameter, so if you have small, cancerous polyps, they could easily be missed without a more intensive procedure like colonoscopy. In medical circles, it is generally recommended that all patients over 50 years old get a regular colonoscopy, not a virtual colonoscopy, once every 10 years. If the patient has a family history of adenomatous polyps or colon cancer, then virtual colonoscopy will almost never be an adequate test.

How Do I Prepare for a Virtual Colonoscopy?

Before the virtual colonoscopy, a patient must refrain from eating solid foods for 24 hours and drink several liters of laxative solution designed to encourage diarrhea and empty the bowels for the exam. This is the worst part of any colon screening test, according to many patient testimonies. However, if there are any feces in the colon during the exam, the virtual colonoscopy might accidently produce a false diagnosis of polyps or other abnormal growths. Stool in the colon can also hide polyps along the bowel wall that are small or flat.

Contact a medical doctor in your area if you are due for a colon cancer screening. While virtual colonoscopies are a great option, you need to discuss your personal medical history with your doctor in order to determine whether virtual colonoscopy will produce a thorough enough examination and accurate results.


Reviewed 12/29/2011 by David M. Nolan, M.D.
Diplomate of the American Board of Internal Medicine, 2011
Currently a Fellow of Gastroenterology, at UCI 2011-2014