Skip to Main Content

Virtual Colonoscopy

  • A CT scan is used to screen for polyps and masses in the large intestine or colon
  • Screens for polyps and masses in the large intestine and colon
  • Traditional colonoscopy may be next step
  • Involves radiology & biomedical imaging


A virtual colonoscopy uses computed tomography (CT) scanning to screen for polyps and masses in the large intestine or colon that could be precancerous or cancerous. Yale Medicine’s radiologists interpret these images and generate a consultation report on the findings that an ordering provider can review.

Jay Pahade, MD, a radiologist, says the state-of-the-art CT scanner that Yale Medicine radiologists use for the procedure has been designed and calibrated to take the clearest possible images of the colon using the least amount of radiation possible.

At Yale Medicine Department of Radiology & Biomedical Imaging, “We’re focusing the scan on the interior of the colon and not the other organs in the abdomen/pelvis,” he says. “So we’re able to use substantially less radiation than most CT scans require.”

Who is a candidate for virtual colonoscopy?

Because insurance coverage for virtual colonoscopy as a routine screening is not universal in Connecticut, Yale Medicine performs the procedure mostly in cases where a traditional colonoscopy isn’t possible.

“A traditional colonoscopy might fail for multiple reasons,” Dr. Pahade says. “A person may have a difficult colon with a lot of twists and turns. Other people don't tolerate the procedure very well. Insurance usually covers a virtual colonoscopy in these cases.”

Dr. Pahade adds, “For people who are not able to undergo sedation or for people taking prescribed medication such as blood thinners, the traditional colonoscopy procedure may be too high risk."

What should you expect?

A patient getting a virtual colonoscopy will complete a normal bowel cleaning preparation like a traditional colonoscopy before the exam. Next, the person will lie on the CT scanner table, where a technologist will insert a flexible tube into the rectum and gently inflate the colon with gas to distend the colon.

The patient will be asked to hold still as the table is moved through the doughnut-shaped CT scanner as the images are acquired. Next, it's time to turn over onto the stomach or side, so the scan can be repeated.

“Even though a person might feel a bit full with the gas used, it's relatively comfortable during the scanning, which takes less then a minute,” says Dr. Pahade. "In fact, the total procedure is usually completed in about 15 minutes."

What are the risks and limitations?

A virtual colonoscopy is much less invasive than a traditional one, and the risk of injury is very low. Even though the CT scan exposes the patient to some radiation, the dose is significantly less than a traditional CT scan. Because of radiation exposure, the procedure is generally not recommended for pregnant women.

If any potential polyps or masses are discovered by the radiologist reading a scan, then the patient may need to complete a traditional colonoscopy to have them removed.

When can a patient expect the results?

After the procedure, the images are sent to a radiologist for review and interpretation. The results are available within 24 hours of a scan, and they’ll be sent to the provider who ordered the study.

What makes Yale Medicine’s approach to virtual colonoscopy unique?

“We have very high end technology, and a very modern CT scanner, using a low-dose technique specifically designed and calibrated for virtual colonoscopy,” Dr. Pahade says. “Perhaps most importantly, we have an extremely knowledgeable and specialized team of radiologists interpreting these unique scans."