About colonoscopy

A colonoscopy is a procedure to visually examine the bowel. People who receive a positive screening result will generally be referred for a colonoscopy.

Page last updated: 15 October 2014

The day before

The day before the colonoscopy you will be asked to drink a special preparation to help empty your bowel. This is important because it helps the doctor see the lining of your bowel more clearly and find any changes.

The day of the procedure

A sedative is given to relax you and will make you feel drowsy. A thin, flexible tube with a tiny camera attached (a colonoscope) is then passed into the rectum. The camera lets the doctor look for polyps or cancerous growths the bowel. The test itself takes about 20 to 30 minutes and you will usually be able to go home about two hours later after the effect of the sedation wears off.

If polyps are seen, the doctor will usually remove them immediately and test them for any abnormal cells that might be cancerous.

About four in 10 people who have a colonoscopy will have a clear result.

About five in 10 will be found to have a polyp, which if removed may prevent cancer developing.

About one in 10 people will be found to have cancer when they have a colonoscopy.

Are there any risks from a colonoscopy?

A colonoscopy is the best way to diagnose bowel cancer and for most people it is a straightforward test. But, as with most medical tests, complications may occur.

Serious complications may include perforation (making a hole) in the bowel wall (about one in 1,000 tests) and/or major bleeding from the bowel (about three in 1,000 tests).

People may also react poorly to the bowel preparation and/or to the sedatives/anaesthetic. Rare side effects can occur with any medical test. Death is a remote possibility (one in 10,000 cases).

As with any medical test, you should discuss the risks and benefits of colonoscopy with your doctor before consenting to the procedure.

What happens if a bowel cancer is detected?

You will usually require surgery if bowel cancer is found. If the cancer is found at an early stage, the chance of a full recovery is high. Most people will be able to return to their current lifestyle and activities.

What if the colonoscopy doesn’t show anything?

A clear colonoscopy means that no polyps or cancerous growths were found. This usually means that you have a low risk of developing bowel cancer within the next 10 years.
Your specialist will discuss your result with you and any further testing or future screening required based on your individual circumstances. This may include a return to two-yearly screening using a Faecal Occult Blood Test (FOBT)

In the meantime, if you develop any of the symptoms of bowel cancer, you should see your doctor immediately.

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