Cookies on the Bupa website

We use cookies to help us understand ease of use and relevance of content. This ensures that we can give you the best experience on our website. If you continue, we'll assume that you are happy to receive cookies for this purpose. Find out more about cookies



Virtual colonoscopy

Virtual colonoscopy is a procedure performed to check your large bowel (your colon and rectum). It’s used to check for small growths called polyps, signs of bowel cancer and other diseases. It’s also known as computed tomography (CT) colonography or CT colonoscopy.

You may have a virtual colonoscopy if you have symptoms such as bleeding or mucus in your faeces (poo). Or it may be to screen, if you’re at high risk of developing bowel cancer or polyps. If you’ve had a conventional colonoscopy and your doctor wasn’t able to see your entire bowel, they may recommend a virtual colonoscopy.

The procedure can check whether you have polyps or other abnormalities on the wall of your bowel. Small polyps are usually harmless and stay that way. However, a certain type, called adenomas, can sometimes develop into cancer if they are large or left to grow.

Virtual colonoscopy is performed using a CT scanner, which uses X-rays to produce two- or three-dimensional images of your bowel. You’ll have a thin tube inserted into your rectum to put gas or air in your bowel. A CT scanner then produces images of your bowel.

You’ll meet the doctor carrying out your procedure to discuss your care. It may be different from what’s described here as it will be designed to meet your individual needs.

Read more Close


  • Alternatives What are the alternatives to virtual colonoscopy?

    There are other procedures that can be used to look at your bowel. The main ones are listed below.

    • Conventional colonoscopy. With conventional colonoscopy, your doctor looks inside your large bowel using a long, flexible, illuminated, telescopic camera. This camera, called a colonoscope, is inserted through your anus.
    • Flexible sigmoidoscopy. This is a similar procedure to colonoscopy, but uses a shorter telescopic camera called a sigmoidoscope. It looks inside your rectum and the lower part of your bowel only (because most bowel cancers develop in this area).
    • Rigid sigmoidoscopy. This procedure uses an instrument shorter than the camera used in flexible sigmoidoscopy and looks at your rectum only.
    • Barium enema. This test involves placing a fluid containing barium (a substance which shows up on X-rays) into your bowel via your anus. X-ray images of your abdomen (tummy) then show the inside of your bowel more clearly.

    Conventional colonoscopy and barium enema are used more often than virtual colonoscopy. However, virtual colonoscopy is less invasive than conventional colonoscopy. Have a chat with your doctor about the options available to you.

  • Preparation Preparing for a virtual colonoscopy

    Virtual colonoscopy is usually carried out in the CT scanning department of the hospital. At least a few days beforehand, you’ll be given information about how to prepare for your visit.

    Usually, your bowel needs to be empty during the test so that the CT scanner can produce clear pictures of your bowel. You may need to follow a special diet for up to three days before your test. This is likely to involve cutting down on solid food and drinking enough clear liquids. You’ll also be asked to take a laxative the day before the procedure to completely empty your bowel.

    Alternatively, your doctor may ask you to take an iodine-based fluid for a couple of days before your test. This is taken with meals for about two days before your test. The fluid helps to show your bowel more clearly on the scan. If you have asthma or an allergy to iodine, you must let your doctor know beforehand.

    It’s important that you tell your doctor about any medicines you're taking and if you are, or could be, pregnant. Virtual colonoscopy, like all X-ray tests, isn’t recommended for pregnant women, unless there’s an urgent medical reason.

    Your doctor will discuss with you what will happen before, during and after your procedure, and any pain you might have. This is your opportunity to understand what will happen. You can help yourself by preparing questions to ask about the risks, benefits and any alternatives to the procedure. This will help you to be informed, so you can give your consent for the procedure to go ahead. You may be asked to give your consent by signing a consent form.

    If you have any last minute questions about how to prepare for the procedure, contact the clinic where you’ll have your test.

  • The procedure What happens during a virtual colonoscopy?

    Virtual colonoscopy is usually carried out in the CT scanning department of the hospital. You’ll have the test and go home on the same day. The procedure usually takes about 10 to 15 minutes.

    A radiologist (a doctor who specialises in using imaging methods to diagnose medical conditions) will carry out the test.

    You’ll be asked to change into a hospital gown and lie on the scanning table. Your doctor may give you an injection of a medicine that will help to relax the muscles of your bowel wall. You may also have an injection of a dye (contrast medium) at the same time. This helps to show up your bowel more clearly on the X-rays. You’ll be given this through a drip placed into a vein in the back of your hand.

    Your doctor will gently pass a thin tube a few centimetres into your rectum. They will then pump a small amount of carbon dioxide or air into your bowel. This will inflate your bowel so that it can be seen more easily on the X-ray. You may feel some slight discomfort when this happens, but few people experience a lot of pain.

    The table will move into the tunnel of the CT scanner so that the middle part of your body is lying in the centre. You’ll have scans taken when you’re lying on your back and others taken when you’re lying on your front or side. At certain points during the scan you may be asked to hold your breath for a few seconds. It can take several minutes for each image to form so it’s important that you lie very still during the scan.

  • Worried about your colon health?

    Get a picture of your current health and potential future health risks with a Bupa health assessment. Find out more today.

  • Aftercare What to expect afterwards

    After your virtual colonoscopy, you’ll be able to go home when you feel ready.

    If you’ve had an injection of contrast medium, you’ll need to wait for an hour before you can drive as it can blur your vision. Your results are usually sent in a report to the doctor who requested your scan. This may take a few days.

    Virtual colonoscopy is used to help diagnose your condition rather than to treat it. If the test shows that you have polyps, you’ll need to have another procedure, for example a conventional colonoscopy, to remove them. See our FAQs for more information.

    If you’re found to have large polyps or cancer, you may need to have surgery. You may also need to have another procedure if the virtual colonoscopy wasn’t able to find the cause of your symptoms.

  • Recovery Recovering from a virtual colonoscopy

    After your virtual colonoscopy, you’ll be able to return to your usual activities straight away. This is because you don’t usually need painkillers or sedation for a virtual colonoscopy.

    It’s possible that you’ll feel bloated and as though you have trapped wind for a short time. This is due to the air that was pumped into your bowel. You may pass gas. You may also have some abdominal pain but this is rare and doesn’t usually last long. You can go back to eating a normal diet after the procedure unless advised otherwise.

  • Risks What are the risks?

    As with every procedure, there are some risks associated with virtual colonoscopy. We haven’t included the chance of these happening as they are specific to you and differ for every person. Ask your doctor to explain how these risks apply to you.

    CT scanners use X-rays to produce images, so you will be exposed to some radiation. This is about the same amount as the natural radiation that you get from the atmosphere over about three years.

    If you are, or think you could be, pregnant, you shouldn't have a CT scan as there is a risk that the radiation may harm your unborn baby.


    Side-effects are the unwanted but mostly temporary effects you may get after having the procedure. The main side-effects of virtual colonoscopy are:

    • pain or discomfort when the air or carbon dioxide is put into your bowel
    • a feeling of warmth when you have an injection of contrast medium
    • blurred vision from the medicine used to relax your bowel


    Complications are when problems occur during or after the procedure. Complications from virtual colonoscopy are uncommon.

    Very rarely, it's possible to have an allergic reaction to the contrast medium. Tell your doctor if you’ve had a reaction to contrast medium in the past. If you feel unwell or have problems breathing during the test, tell your doctor straight away.

    There is a very small chance that your bowel may be damaged or torn when air or carbon dioxide is put in during the procedure. This is very rare and happens to fewer than one in 10,000 people who have a virtual colonoscopy. If your bowel is damaged, it can lead to bleeding and infection and you may need surgery to repair it.

  • FAQs FAQs

    What will happen if a polyp is found during my virtual colonoscopy?


    Polyps are small growths that can develop inside your bowel. They’re quite common and don’t usually cause any problems. However, in some people polyps can grow into cancer over time. So, if the results of your virtual colonoscopy show you have polyps, your doctor will discuss with you whether they need to be removed.


    Polyps are growths that can occur inside your bowel. They are small, fleshy lumps, usually less than 1cm in size, but they can grow to be bigger. Polyps are common. About one in four people will have a polyp at some time in their lives, most often after the age of 60.

    Some polyps are attached to the side of your bowel on a stalk and look a bit like a mushroom. Others are flatter and have no stalk. You may have just one polyp or several.

    Most polyps don’t cause any problems. There’s a small chance that over a long period of time a certain type of polyp called an adenoma will grow into a cancer. An adenoma that’s over 1cm in size has almost a one in 10 risk of containing cancer cells.

    If your virtual colonoscopy shows that you have a polyp, your doctor may suggest that you have it removed. This is usually done during a conventional colonoscopy.

    After your polyp is removed it will be sent to a laboratory. This is to find out exactly what type it is and whether any of the cells show signs of cancer or might have developed into cancer in the future. Depending on the results, you may need to go back to hospital for more treatment or further tests.

    Some people are at higher risk of getting polyps. If you develop polyps a number of times, your doctor may advise you to have check-ups with conventional colonoscopy every few years.

    What’s the difference between a virtual colonoscopy and a conventional colonoscopy?


    Conventional colonoscopy and virtual colonoscopy are both procedures that enable your doctor to look at your large bowel (your colon and rectum). One important difference is that during a conventional colonoscopy your doctor can remove any polyps found, or take a biopsy.


    There are a number of differences between conventional and virtual colonoscopy.

    During a conventional colonoscopy your doctor looks at the inside of your bowel using a narrow, flexible, tube-like, telescopic camera called a colonoscope. You’ll usually have a sedative during the procedure to relieve any anxiety and help you to relax.

    In contrast, virtual colonoscopy takes images from outside your body, using a CT scanner, and you won’t usually need a sedative. It’s less invasive because less of the procedure involves instruments being used internally. Virtual colonoscopy can be quicker compared to conventional colonoscopy. You may find virtual colonoscopy more comfortable, but this can vary from person to person.

    If you have a conventional colonoscopy, your doctor can pass thin instruments through the colonoscope to remove polyps or to take biopsies if needed. This isn't possible during a virtual colonoscopy. If your doctor finds any polyps or possible tumours with a virtual colonoscopy, you may need a conventional colonoscopy afterwards to have them removed.

    With conventional colonoscopy, there’s slightly more risk of your bowel being damaged during the procedure.

    Sometimes, it isn’t always possible to see all of your bowel with a conventional colonoscopy (for example if the camera cannot pass through the whole bowel). This isn’t a problem with virtual colonoscopy. Another advantage of virtual colonoscopy is that it may be safer if:

    • you’re elderly or frail
    • your bowel is blocked
    • you’re taking a medicine to thin your blood, such as warfarin

    Some patients find virtual colonoscopy more convenient and prefer this procedure.

    It’s important to remember that virtual colonoscopy is carried out using a CT scanner. This uses X-rays to produce images, so you’ll be exposed to some radiation. This doesn’t happen during a conventional colonoscopy.

    The investigation that’s best for you will depend on your general health, your symptoms and what your doctor thinks may be causing them. Your doctor will discuss with you the different types of tests available.

    How accurate is a virtual colonoscopy compared with other investigations?


    Virtual colonoscopy is a relatively new procedure so there’s less information available about how accurate it is than for some other procedures. However, based on studies, experts believe virtual colonoscopy is safe and works well.


    Research has looked at how accurate a virtual colonoscopy is at detecting bowel cancer or polyps compared with a barium enema and a conventional colonoscopy.

    The research shows that a virtual colonoscopy may not detect all small or flat polpys, but this is true of other procedures too. For example, a study found that virtual colonoscopy found large polyps (bigger than 1cm) in nine out of 10 patients who had them. However, it found small polyps (smaller than half a centimetre) in only six or seven out of every 10 patients who had them. This accuracy was similar to that with conventional colonoscopy.

    Overall, experts agree that virtual colonoscopy is safe and works well.

    If you need to have repeat check-ups for polyps, usually this will be done with conventional colonoscopy.

    All of the investigations for bowel cancer and polyps have benefits and risks. Your doctor will discuss these so that you can find out which one is most suitable for you.

  • Resources Resources

    Further information


    • Computed tomographic colonography (virtual colonoscopy). National Institute for Health and Clinical Excellence (NICE), 2005.
    • Bowel cancer. Cancer Research UK., published August 2013
    • Map of Medicine. Colorectal cancer. International View. London: Map of Medicine; 2014 (Issue 4)
    • Colonic polyps. Medscape., published October 2014
    • Virtual colonoscopy. National Digestive Diseases Information Clearinghouse (NDDIC)., published September 2013
    • Computed tomographic colonography (virtual colonoscopy): Understanding NICE guidance – information for people considering the procedure, and for the public. National Institute for Health and Clinical Excellence (NICE), 2005.
    • Bowel cancer. Macmillan Cancer Support., published January 2013
    • Pox CP, Schmiegel W. Role of CT colonography in colorectal cancer screening: risks and benefits. Gut 2010;59(5):692−700. doi: 10.1136/gut.2009.183046
  • Has our information helped you? Tell us what you think about this page

    We’d love to know what you think about what you’ve just been reading and looking at – we’ll use it to improve our information. If you’d like to give us some feedback, our short form below will take just a few minutes to complete. And if there's a question you want to ask that hasn't been answered here, please submit it to us. Although we can't respond to specific questions directly, we’ll aim to include the answer to it when we next review this topic.

    Let us know what you think using our short feedback form
    Ask us a question
  • Related information Related information

  • Author information Author information

    Reviewed by Dylan Merkett, Bupa Health Content Team, January 2015

    Let us know what you think using our short feedback form
    Ask us a question

About our health information

At Bupa we produce a wealth of free health information for you and your family. We believe that trustworthy information is essential in helping you make better decisions about your health and care. Here are just a few of the ways in which our core editorial principles have been recognised.

  • Information Standard

    We are certified by the Information Standard. This quality mark identifies reliable, trustworthy producers and sources of health information.
    Information standard logo
  • HONcode

    This site complies with the HONcode standard for trustworthy health information: verify here.

    This website is certified by Health On the Net Foundation. Click to verify.

What our readers say about us

But don't just take our word for it; here's some feedback from our readers.

Simple and easy to use website - not alarming, just helpful.

It’s informative but not too detailed. I like that it’s factual and realistic about the conditions and the procedures involved. It’s also easy to navigate to areas that you specifically want without having to read all the information.

Good information, easy to find, trustworthy.

Meet the team

Nick Ridgman

Nick Ridgman
Head of Health Content

  • Dylan Merkett – Lead Editor
  • Natalie Heaton – Specialist Editor, User Experience
  • Pippa Coulter – Specialist Editor, Content Library
  • Alice Rossiter – Specialist Editor, Insights
  • Laura Blanks – Specialist Editor, Quality
  • Michelle Harrison – Editorial Assistant

Our core principles

All our health content is produced in line with our core editorial principles – readable, reliable, relevant – which are represented by our diagram.

An image showing or editorial principals

                  Click to open full-size image

The ‘3Rs’ encompass everything we believe good health information should be. From tweets to in-depth reports, videos to quizzes, every piece of content we produce has these as its foundation.


In a nutshell, our information is jargon-free, concise and accessible. We know our audience and we meet their health information needs, helping them to take the next step in their health and wellbeing journey.


We use the best quality and most up-to-date evidence to produce our information. Our process is transparent and validated by experts – both our users and medical specialists.


We know that our users want the right information at the right time, in the way that suits them. So we review our content at least every three years to keep it fresh. And we’re embracing new technology and social media so they can get it whenever and wherever they choose.

Our accreditation

Here are just a few of the ways in which the quality of our information has been recognised.

  • The Information Standard certification scheme

    You will see the Information Standard quality mark on our content. This is a certification programme, supported by NHS England, that was developed to ensure that public-facing health and care information is created to a set of best practice principles.

    It uses only recognised evidence sources and presents the information in a clear and balanced way. The Information Standard quality mark is a quick and easy way for you to identify reliable and trustworthy producers and sources of information.

    Certified by the Information Standard as a quality provider of health and social care information. Bupa shall hold responsibility for the accuracy of the information they publish and neither the Scheme Operator nor the Scheme Owner shall have any responsibility whatsoever for costs, losses or direct or indirect damages or costs arising from inaccuracy of information or omissions in information published on the website on behalf of Bupa.

  • British Medical Association (BMA) patient information awards

    We have received a number of BMA awards for different assets over the years. Most recently, in 2013, we received a 'commended' award for our online shared decision making hub.

Contact us

If you have any feedback on our health information, we would love to hear from you. Please contact us via email: Or you can write to us:

Health Content Team
Bupa House
15-19 Bloomsbury Way

Find out more Close

Legal disclaimer

This information was published by Bupa's Health Content Team and is based on reputable sources of medical evidence. It has been reviewed by appropriate medical or clinical professionals. Photos are only for illustrative purposes and do not reflect every presentation of a condition.

The information contained on this page and in any third party websites referred to on this page is not intended nor implied to be a substitute for professional medical advice nor is it intended to be for medical diagnosis or treatment. Third party websites are not owned or controlled by Bupa and any individual may be able to access and post messages on them. Bupa is not responsible for the content or availability of these third party websites. We do not accept advertising on this page.

For more details on how we produce our content and its sources, visit the 'About our health information' section.

ˆ We may record or monitor our calls.