Virtual Colonoscopy

A virtual colonoscopy is a CT scan that looks for polyps or cancer in your colon and rectum. This test uses highly detailed, 3D images to see the entire length of your colon, and you don’t need sedation.


What is a virtual colonoscopy?

A virtual colonoscopy is an X-ray that looks for polyps (growths), ulcers (sores) and cancer in your colon and rectum. Your colon and rectum are tube-like organs that are part of your large intestine, and they help digest food. A virtual colonoscopy is also called a computerized tomography (CT) colonography.


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When is a virtual colonoscopy performed?

Health experts recommend everyone get a screening for colorectal cancer starting at age 45. If you have a higher risk for colorectal cancer, you may need screening at a younger age. Risk factors for colorectal cancer include:

Virtual colonoscopy is one option for colorectal cancer screening. Your provider may recommend another test, such as a traditional colonoscopy or a stool test.

Virtual colonoscopy vs. traditional colonoscopy: What’s the difference?

A traditional colonoscopy is different from a virtual colonoscopy in a few ways:

  • Ability to remove polyps: Your provider can remove polyps during a traditional colonoscopy, but not during a virtual colonoscopy. If your provider sees polyps during a virtual colonoscopy, you need a follow-up traditional colonoscopy to remove them.
  • Anesthesia: Traditional colonoscopy requires sedation or anesthesia, so you’ll be relaxed or asleep during the procedure. A virtual colonoscopy doesn’t require sedation or anesthesia, so you can resume your regular activities right after the test.
  • Length of test: A colonoscopy takes up to 90 minutes, and sometimes longer if your provider removes polyps. A virtual colonoscopy usually takes about 15 minutes.
  • Imaging tools: A traditional colonoscopy uses a colonoscope (camera attached to a long, flexible tube) to look inside your colon. A virtual colonoscopy uses images from a CT scan, and the pictures are taken from outside your body.


Who performs a virtual colonoscopy?

A trained X-ray technician performs your virtual colonoscopy and gathers all the images. Then, a radiologist (a medical doctor who specializes in medical imaging) looks at the images and checks for colon polyps, ulcers or spots that could be cancer or precancerous.

Test Details

How do I prepare for a virtual colonoscopy?

Before your virtual colonoscopy, you’ll do a bowel preparation, or “prep.” This process empties your colon of all stool, so your provider can see your colon and rectum clearly. Your prep for a virtual colonoscopy is similar to the prep you’d do for a traditional colonoscopy. You usually do your prep the day before your virtual colonoscopy.

Your provider will give you instructions on how to complete your virtual colonoscopy bowel prep, which may include:

  • Enemas: Medicines you put in your rectum to stimulate bowel movements.
  • Laxatives: Liquids or powders that make you have frequent bowel movements.
  • Clear liquid diet: The day before your procedure, you may not be able to eat or drink anything other than clear liquids like water, fat-free broth, apple juice and plain coffee or tea. Your provider will give you a list of things you can eat and drink during your prep.
  • Fasting: You won’t be able to eat or drink for a few hours before your procedure.
  • Drinking a contrast medium: This liquid helps your provider see your colon clearly on the virtual colonoscopy.

A complete bowel prep is necessary for a successful virtual colonoscopy. It will cause frequent and watery diarrhea, so plan to stay at home and near a bathroom during your prep period.


What happens during a virtual colonoscopy?

The day of your appointment, wear comfortable clothing and don’t wear any jewelry. The X-ray technician will take you to a room with the CT scanner, which looks like a large, donut-shaped machine. Your virtual colonoscopy usually involves these steps:

  1. After changing into a hospital gown, you lie down on a table.
  2. The technician inserts a short tube about 2 inches into your rectum. This tube gently pumps some air into your colon, which inflates it and makes it easier to see details.
  3. The table slowly slides you into the CT scanner, which looks like a short tunnel. The CT scanner makes buzzing or clicking sounds as it takes pictures of your colon.
  4. You lie very still while the CT scanner takes pictures. The technician talks to you throughout the process using an intercom system. They may ask you to hold your breath for a few seconds or to change positions during the test.
  5. After your test is done, the table slides you out of the scanner, they remove the tube from your rectum and you get dressed.

What should I expect after a virtual colonoscopy?

After your virtual colonoscopy, you can go back to normal activities and eat and drink normally. Because it doesn’t require anesthesia, virtual colonoscopy usually has very little or no recovery time.

You may have some excess gas from the air that was pumped into your colon. This is normal, and the gas may cause some cramping or bloating. Usually, this is not severe.

What are the benefits of a virtual colonoscopy?

Benefits of a virtual colonoscopy include:

  • Clear, detailed 2D and 3D images as clear as what a provider can see on a traditional colonoscopy.
  • Faster recovery, because you don’t have sedation.
  • Less invasive, because providers don’t have to insert a scope into your colon.
  • Lower risk of injury to the colon than traditional colonoscopy.
  • Suitable for people who can’t have sedation or traditional colonoscopy.
  • Takes pictures of your entire bowel, even if you have a bowel obstruction or narrowed parts in your bowel.

What are the risks of a virtual colonoscopy?

A virtual colonoscopy uses X-rays, which expose you to a small amount of radiation. Large amounts of radiation over time increase the risk of cancer. However, the amount of radiation from a virtual colonoscopy is small. Experts believe the benefits of detecting colon cancer outweigh this risk.

There’s also a small risk of bowel perforation (tear in your bowel) from inflating your bowel with air. However, the risk of bowel perforation is lower in a virtual colonoscopy compared to a traditional colonoscopy.

You shouldn’t have a virtual colonoscopy if you’re pregnant or could be pregnant. In addition, the contrast medium can interact with some medications and may not be safe for people with certain health conditions. Before scheduling your virtual colonoscopy, tell your provider:

  • About all medications you take, including vitamins and supplements.
  • If you’re pregnant or think you might be pregnant.
  • Whether you have any health conditions or allergies.

Results and Follow-Up

What do my virtual colonoscopy results mean?

If your provider finds an abnormality or a polyp on your virtual colonoscopy, this doesn’t mean you have colorectal cancer. However, you will need a follow-up colonoscopy so your provider can remove the polyp or abnormality.

In some cases, your provider can perform a colonoscopy right after your virtual colonoscopy. This can be helpful if your provider needs to remove something and you’ve already completed your bowel prep. Or, you may need to schedule your colonoscopy for a later date.

If your results are normal, ask your provider when you should have your next colorectal cancer screening. If you have a low risk of colorectal cancer, you may need a repeat virtual colonoscopy every five years.

When should I call my doctor?

Seek medical care right away if you notice these symptoms after your virtual colonoscopy:

A note from Cleveland Clinic

Colorectal cancer is the third most common cancer in U.S. adults, excluding skin cancers. Colorectal screening tests can catch this cancer early when it’s easier to treat. Still, many people don’t get the screening they need because they don’t want a colonoscopy.

With a low risk of complications and a faster recovery, a virtual colonoscopy is a good alternative to traditional colonoscopy for many people. Talk to your healthcare provider about your colorectal screening options to find out which test is right for you.

Medically Reviewed

Last reviewed on 04/20/2022.

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