What is a virtual colonoscopy?

A virtual colonoscopy is a CT (computed tomography) or MRI (magnetic resonance imaging) scan of the colon and rectum. CT relies on X-rays to generate the image and MRI uses a different type of technology not involving X-rays. Your doctor may recommend a virtual colonoscopy to screen for colon cancer and possibly look for other diseases of the colon. A virtual colonoscopy is an important test that can help detect colorectal cancer in its earliest, most curable stage and other serious conditions.

The colon and the rectum make up the large intestine, sometimes called the large bowel. The large intestine is a long, hollow organ in your abdomen that plays an important role in digestion by removing water from digested material and forming feces. In addition to looking for signs of colorectal cancer, a virtual colonoscopy can help your doctor find the reason for unexplained intestinal symptoms you may be having, such as changes in your bowel movements, abdominal pain, or rectal bleeding.

Virtual colonoscopy, also known as a CT colonography, is only one method used to screen for colon cancer. A conventional colonoscopy is also used to screen for colon cancer and to help detect other diseases of the colon. A colonoscopy is a more invasive procedure that allows your doctor to see the lining of your colon and rectum using a thin, flexible instrument with a camera, called a colonoscope. This instrument is inserted through the rectum into the colon. 

Certain procedures can be done during a colonoscopy that cannot be performed during a virtual colonoscopy. These include taking a biopsy, controlling bleeding, and removing polyps (growths that can become cancerous). You should discuss all of your diagnostic and colon cancer screening options with your doctor or healthcare provider to best understand which option is right for you.

Why is a virtual colonoscopy performed? 

Your primary care doctor or a gastroenterologist may recommend a virtual colonoscopy to screen for colon cancer and colon polyps, growths that can become cancerous. Your doctor may also recommend the procedure to help diagnose a variety of other diseases and conditions of the colon and rectum including:

  • Abdominal pain, which can be caused by many different conditions including inflammatory bowel disease, diverticulitis, and intestinal ulcer
  • Abnormal changes in your bowel movements, which can be caused by a variety of conditions from intestinal inflammation to colon cancer
  • Anemia (low red blood cell count) if the underlying cause has not been found through less invasive testing. A virtual colonoscopy may be used to identify potential bleeding sites.
  • Bleeding symptoms, such as bloody stool, or black, tarry feces. Potential causes of such bleeding include colon cancer and intestinal inflammation or damage.
  • Poor colonoscopy results, such as the inability to see the entire colon during a traditional colonoscopy.

Who performs a virtual colonoscopy?

Radiologists and diagnostic radiologists perform virtual colonoscopies. Radiologists specialize in using radiation and other imaging techniques to diagnose and treat a wide variety of conditions from broken bones and birth defects to cancer. Diagnostic radiologists specialize in performing and interpreting imaging tests, such as ultrasounds, X-rays, angiograms, CTs, nuclear scans, and MRIs.

A radiologic technologist may perform the actual procedure under direction from the radiologist or diagnostic radiologist.

How is a virtual colonoscopy performed?

A virtual colonoscopy is performed in a hospital radiology department or outpatient radiology clinic. It takes about 30 minutes and generally includes these steps:

  1. You dress in a patient gown and lie on an examination table.
  2. The radiologic technologist positions you on the table and inserts a small flexible tube about two inches into your rectum.
  3. Air is pumped into the colon. This expands the colon to help create the clearest images of the entire organ. 
  4. The table you’re lying on moves you through a tunnel-like structure as a series of images are taken. You may be placed in a variety of positions during this process. You will also need to hold your breath briefly during the procedure to help avoid blurry images.
  5. After all the images have been taken, you will wait briefly while the pictures are checked for quality.