Virtual colonoscopy Q&As
Published by Bupa's health information team, July 2009.
Answers to questions about virtual colonoscopy
This section contains answers to common questions about this topic. Questions have been suggested by health professionals, website feedback and requests via email.
- What will happen if a polyp is found on my virtual colonoscopy?
- What's better - a virtual colonoscopy or a conventional colonoscopy?
- Compared to other investigations, how accurate is a virtual colonoscopy?
What will happen if a polyp is found on my virtual colonoscopy?
Polyps are growths inside your bowel. They are quite common and rarely cause any problems. However, in some people polyps can grow into cancers over time. So if your doctor sees polyps at your virtual colonoscopy, especially larger ones, he or she will usually discuss with you whether they need to be removed.
Explanation
A polyp is a growth inside your bowel. These are small lumps, usually less than 1cm in size, although occasionally they are larger. They are relatively common - around one in every four people develops a polyp at some time in their life.
Some polyps are attached to the side of your bowel on a stalk and look a bit like a mushroom, whereas others are flatter and have no stalk. You may have just one polyp or two or more. Most polyps never cause any problems at all.
However, there is a small chance that over a long period of time, a polyp will grow into a cancer. A polyp that is 1cm in size has about a one in six chance of developing into a cancer over a 10-year period. Therefore, if your virtual colonoscopy shows signs of any polyps, your doctor will consider following this with either a conventional colonoscopy or a sigmoidoscopy to remove them. If the polyp is very small, you may need to have another virtual colonoscopy at a later date to check that it hasn't increased in size.
After the polyp is removed it will be sent to a laboratory to be looked at under a microscope. This is to see whether any of the cells show signs of cancer or look like they might develop into cancer in the future. Depending on the results you may need to go back to hospital for more treatment or further tests.
Further information
- CORE (The Digestive Disorders Foundation)
020 7486 0341
www.corecharity.org.uk
Sources
- Polyps in the bowel. CORE. www.corecharity.org.uk, accessed 15 February 2009
- High risk groups for bowel cancer. Cancer Research UK. www.cancerhelp.org.uk, accessed 15 February 2009
- Flexible sigmoidoscopy. British Society of Gastroenterology. www.bsg.org.uk, accessed 15 February 2009
- Tests for bowel cancer. Cancer Research UK. www.cancerhelp.org.uk, accessed 15 February 2009
What's better - a virtual colonoscopy or a conventional colonoscopy?
Conventional and virtual colonoscopy are both investigations that allow your doctor to look at your large bowel (the colon). In conventional colonoscopy, images of your bowel lining are taken using a narrow, flexible, tube-like camera called a colonoscope which is passed into your colon and rectum. With virtual colonoscopy pictures are taken from outside your body using X-rays and a scanner. Conventional colonoscopy also allows your doctor to take samples of your bowel (biopsies) or remove polyps at the same time if necessary.
Explanation
There are a number of differences between conventional and virtual colonoscopy. Conventional colonoscopy is called an invasive investigation because the equipment goes inside your body during the procedure. You will be given a sedative before the procedure - this relieves anxiety, allows you to relax, and helps with any discomfort. With a conventional colonoscopy you're slightly more at risk of some rare complications that aren't usually associated with a virtual one. Some of these include:
- bleeding after the procedure
- a tear in your bowel
- problems with the medicine used for sedation
If you have a virtual colonoscopy, you're at a small risk from the exposure to radiation used during the procedure. You won't need a sedative before having a virtual colonoscopy.
It's hard to say whether having a virtual colonoscopy is more comfortable than having a conventional one as studies have produced conflicting evidence. Doctors think that people having conventional colonoscopy may find it more comfortable than virtual colonoscopy. This is because of the sedation that is given during this procedure to help patients to relax.
If you have a conventional colonoscopy and your doctor finds any polyps, he or she can remove them during the same procedure. Your doctor can also take samples of your bowel for testing in a laboratory. However, it isn't possible to take samples or remove polyps during a virtual colonoscopy. So if your doctor sees any, you will probably need to go back to hospital for a conventional colonoscopy at a later date to have these removed.
Further information
- British Society of Gastroenterology
www.bsg.org.uk
Sources
- Colonoscopy. British Society of Gastroenterology. www.bsg.org.uk, accessed 15 February 2009
- Bowel cancer screening. The colonoscopy investigation. Cancer Research UK, NHS Cancer Screening Programmes. www.cancerscreening.nhs.uk, accessed 15 February 2009
- Computed tomographic colonography (virtual colonoscopy). National Institute for Health and Clinical Excellence (NICE). www.nice.org.uk, 2005
- Virtual colonoscopy. Radiology Info. www.radiologyinfo.org, accessed 15 February 2009
- Flexible sigmoidoscopy. British Society of Gastroenterology. www.bsg.org.uk, accessed 15 February 2009
Compared to other investigations, how accurate is a virtual colonoscopy?
Virtual colonoscopy is a relatively new investigation. This means that compared to other procedures there is less information available about how accurate it is at finding polyps and cancer.
Explanation
Research has been carried out to find out how accurate a virtual colonoscopy is compared to a barium enema and a conventional colonoscopy. This showed that a virtual colonoscopy produces more reliable results than a barium enema, and similar results to conventional colonoscopy for large polyps, but it may not be as good as a conventional colonoscopy at finding flat and small polyps.
A virtual colonoscopy can show about 95 out of every 100 large polyps. Large polyps are those that are bigger than 10mm across. However, it can be difficult to see small or flat polyps using this test. Virtual colonoscopy can find only about half of all small polyps - those smaller than 5mm. However, small or flat polyps are difficult to see with the other investigations as well.
If, after looking at your symptoms, your doctor thinks there is a high chance you may have cancer or an advanced polyp, he or she is likely to suggest that you have a conventional colonoscopy rather than a virtual one. This is because conventional colonoscopy is more accurate at picking up signs of cancer. It also means your doctor can take a sample of any tumour or polyp that he or she finds.
Each of the investigations for bowel cancer and polyps has benefits and risks. Your doctor will discuss these with you so that you can choose the one that is best for you.
Sources
- Computed tomographic colonography (virtual colonoscopy). National Institute for Health and Clinical Excellence (NICE), www.nice.org.uk, 2005
- Rockey DC, Paulson E, Niedzwiecki D et al. Analysis of air contrast barium enema, computed tomographic colonography, and colonoscopy: prospective comparison. Lancet 2005; 365(9456): 305-11
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This information was published by Bupa's health information team and is based on reputable sources of medical evidence. It has been peer reviewed by Bupa doctors. The content is intended for general information only and does not replace the need for personal advice from a qualified health professional.
Publication date: July 2009
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