Colonoscopy Q&A

Mr Simon Radley is a consultant colorectal surgeon at The Priory Hospital and The Droitwich Spa Hospital. Mr Prateesh Trivedi is a consultant colorectal and general surgeon at The Runnymede Hospital. They talk us through some of the most commonly asked questions about having a colonoscopy, covering how it works as well as risks and side effects.

What is a colonoscopy?

Mr Simon Radley: Colonoscopy is a diagnostic examination of the large bowel. This involves the doctor passing a flexible telescope around the bowel. This allows the doctor see a magnified image of the lining of the bowel directly. Photographs can be taken, tissue samples (known as biopsies) can be taken. Small and sometimes even large polyps can be removed. (Polyps are warty type growths in the bowel, some of which can turn cancerous.)

The doctor who performs your procedure should be able to complete a whole colon examination in at least 90% of people.

Mr Prateesh Trivedi: Colonoscopy is when a flexible fibre optic scope (called a colonoscope) is inserted via the back passage to visualise the lining of the large bowel.

Why is a colonoscopy carried out?

Mr Simon Radley: The most common reason we do a colonoscopy is as a diagnostic test. Usually this is to investigate a cause of bleeding from the bowel or a change in bowel habit. Colonoscopy is also performed as part of the national bowel cancer screening project for people who have positive tests for blood in their stools.

We also perform colonoscopy in patients with a family history of bowel cancer who may be at higher risk than the general population. We also perform colonoscopy at varying intervals for patients who have had previous bowel cancers or certain types of polyps removed. Colonoscopy is also performed to diagnose assess and monitor inflammatory bowel diseases such as ulcerative colitis and Crohn's disease.

Mr Prateesh Trivedi: A colonoscopy is carried out for several reasons. As a diagnostic test, it can look for abnormalities such as bowel cancer or inflammatory bowel disease in patients who, for example, have a change in their bowel habit and/ or rectal bleeding. It can be used as a therapeutic intervention in order to remove abnormalities such as polyps. For surveillance purposes, in patients who have previously had polyps removed or had surgery for bowel cancer. It is also used for screening patients with a high risk of developing bowel cancer and as part of the national bowel cancer screening programme.

What does the procedure involve?

Mr Simon Radley: The procedure involves taking strong laxatives at home the day before. These are used to clear out the bowel completely so that we can get a good view when we do the colonoscopy. The laxatives and the instructions about eating and drinking are sent out to you by post beforehand.

When you come for the colonoscopy, you will have a needle in the back of your hand and we will give you a sedative for the procedure. A colonoscopy takes around 30 minutes to carry out. During this time the doctor will carefully examine the bowel both whilst passing the scope into the bowel and also whilst taking it out.

Biopsies can be taken and polyps can be removed. After a brief period of recovery you will be allowed to eat and drink. Patients are usually able to leave within a couple of hours of the procedure. Your doctor will speak to you before you go.

Mr Prateesh Trivedi: Prior to the day of the procedure the patient is given a strong laxative medication in order to cleanse the bowel to allow good visualisation. The procedure is typically carried out as a day-case procedure under sedation, but can be performed under a general anaesthetic or no sedation at all.

Are there any alternatives to a colonoscopy?

Mr Simon Radley: Yes there are a number of alternatives to colonoscopy. The modern alternatives are a CT scan or a virtual colonoscopy which is another form of CT scan. Neither test is as good as colonoscopy at detecting abnormalities. The other downside of these tests is that no biopsies can be taken nor can any polyps be removed. We tend to use these tests only when a colonoscopy has been unsuccessful or if a patient would not tolerate a colonoscopy for other health reasons.

Barium enema was a frequently performed examination to investigate the bowel but has been virtually completely replaced by colonoscopy or CT scans.

Mr Prateesh Trivedi: The alternatives to colonoscopy are performed in the x-ray department. Barium enemas were the first choice but have now been largely superseded by CT colonography. CT colonography, however, does not reliably identify small polyps. They are utilised in situations in which colonoscopy is not safe, not possible, or when a colonoscopy is incomplete.

Are there any risks or side effects to the procedure?

Mr Simon Radley: Side effects for colonoscopy are rare. The main risks of the procedure are causing bleeding or making a hole in the bowel. Bleeding is uncommon and usually only occurs when tissue is removed. You should always tell your doctor if you are on any medication to thin the blood. The most important risk is making a hole in the bowel. This usually only happens after taking biopsies or removing polyps but may also happen during a purely diagnostic examination.

Mr Prateesh Trivedi: The medication to cleanse the bowel can be unpleasant and it is important to remain well hydrated. During the colonoscopy, there is a risk of making a hole in the bowel called a perforation, and this risk is usually quoted as one in a thousand (1:1000). There is a risk of bleeding, but this typically resolves without the need for any further intervention.

When will I get the results?

Mr Simon Radley: Usually, I will let you know the results as soon as you are 'awake'. I can usually tell you what I have found and if I have any concerns at all. If we remove tissue (biopsies or polyps) we won't get the results back for a few days. I will usually see patients in clinic with those results.

Mr Prateesh Trivedi: The patient is given the result immediately after the colonoscopy. If biopsies have been taken, or polyps removed it can take up to two weeks to get the pathology results back.