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Virtual Colonoscopy

Medically reviewed by Last updated on Dec 2, 2022.

What do I need to know about a virtual colonoscopy?

A virtual colonoscopy is a type of x-ray test to examine the inside of your colon (large intestine). Healthcare providers use a CT scan or MRI to take pictures of your colon from outside your body. This procedure may be used to check for polyps (growths) or cancer. The size of a polyp may also be monitored. You may need this procedure to check if colorectal cancer has come back after you had treatment. A virtual colonoscopy may be used if you are not able to have a regular colonoscopy.

What do I need to do the week before my virtual colonoscopy?

  • Tell your healthcare provider if you know or think you are pregnant. CT scans are not used during pregnancy because of the risk to the unborn baby.
  • Contrast liquid is given to help polyps and other changes show up better in the x-ray pictures. Tell your healthcare provider if you have ever had an allergic reaction to contrast liquid.
  • Talk to your healthcare provider about all the medicines and supplements you take. You will need to stop taking medicines that contain aspirin or iron for 7 days before your colonoscopy. If you take a blood thinner, such as warfarin, ask when you should stop taking it.
  • Tell your healthcare provider if you have any metal in or on your body. If you are having an MRI colonoscopy do not enter the MRI room with anything metal. Metal can cause serious injury.

How should I prepare for my virtual colonoscopy?

Your healthcare provider will have you prepare your bowels before your procedure. Your bowels will need to be empty before your procedure to allow him or her to see your colon clearly.

  • Drink clear liquids 1 to 2 days before your procedure. Clear liquids include plain gelatin, unsweetened fruit juices, clear soup, and broth. Do not drink any liquid that is blue, red, or purple.
  • Do not eat foods that are hard to digest. These include fruits, vegetables, cereal, nuts, peas, beans, popcorn, and tomatoes. Ask your healthcare provider for a list of foods to avoid. If you are having an MRI colonoscopy, you may also need to avoid any food that contains manganese (a metal), such as chocolate.
  • Follow your bowel prep as directed. Many different preparations can be given before a colonoscopy. With any bowel prep, stay close to the bathroom. This liquid will cause you to have bowel movements often.
  • An enema may be needed. Your healthcare provider may tell you to use an enema to help clean out your bowels.
  • Drink contrast liquid the night before your procedure. You will be given the liquid and instructions to follow. Drink the contrast liquid after you finish all of your bowel prep medicine.

What will happen during a virtual colonoscopy?

  • Your healthcare provider may give you medicine that will relax your colon. You will be asked to lie on your left side or on your stomach and raise one or both knees toward your chest. Your healthcare provider will examine your anus and use a gloved finger to check your rectum. Your healthcare provider will gently insert a thin, flexible tube into your rectum. If a CT colonoscopy will be done, air or carbon dioxide will be put into the tube. In an MRI colonoscopy, warm water or solutions with contrast liquid will be passed through the tube and into your colon. This expands your colon to help the doctor see it clearly.
  • During your procedure, the bed you are lying on will be moved inside the CT or MRI tube. Pictures will be taken as the bed or table moves and as you change positions. You may be asked to lie on your back or stomach. If the bowel is not expanded enough, more air or gas will be pumped into your rectum. You will have to hold your breath and stay still as each picture is taken.

What will happen after a virtual colonoscopy?

You may have some cramping or feel bloated after the procedure. You may need to lie on your left side with a heating pad on your abdomen. Eat small meals until the bloating improves.

What are the risks of a virtual colonoscopy?

A virtual colonoscopy may not find certain polyps or other problems in your intestines. Your healthcare provider will not be able to remove growths or take tissue samples to be tested. If contrast liquid is used, it may cause you to have headaches, nausea, vomiting, flushing, or itchiness. You could also have an allergic reaction to the liquid. You may feel a little pain or discomfort as the small tube is placed inside your rectum. Your colon may tear due to increased pressure. If this happens, you will need to stay in the hospital and have surgery on your colon.

Care Agreement

You have the right to help plan your care. Learn about your health condition and how it may be treated. Discuss treatment options with your healthcare providers to decide what care you want to receive. You always have the right to refuse treatment. The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

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Further information

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