What is a colonoscopy?


A colonoscopy is an examination of the large bowel with a flexible scope.  It is usually uncomfortable rather than painful. It takes about half an hour.

What does the colonoscopy involve?

Before the procedure starts, you are given an injection.  It makes you very relaxed but does not put you to sleep.  With this, most people find the procedure easy to tolerate.  We start off with a rectal examination with the finger.  Thereafter the scope is passed.  We inflate air into the colon to distend the bowel to enable us to carefully evaluate the bowel lining.  The scope is passed through the entire large bowel and often into the end of the small bowel on the other side.

 A few people find parts of the procedure sore when there is a tight corner in the bowel.  If this happen, the pain feels like a cramp and I will usually be able to warn you before you feel the cramp.  Sometimes the sister will have to press on the tummy to help get the scope around the corner.  Pain and discomfort in these situations are brief and short lasting.  Some people, especially if they have had several colonoscopies before, prefer no sedative.

What if I have a polyp in the bowel?

If a polyp is found it is usually removed during the colonoscopy.  Polyps are lumps on the lining of the bowel, rather like moles on the skin.  Most are harmless but a few will become cancerous.  Because of this tendency it is usual to remove all except very small polyps.  The base of the polyp is cauterised with an electric current.  This does not hurt.  It stops bleeding and cuts off the polyp for microscopic examination.

What if we find other abnormalities in the bowel?

Sometimes we find other abnormalities which cannot be completely removed like a polyp.  We then take a small piece of the abnormal lining in the bowel (called a biopsy) and send this away for tests.  Under some circumstances we will even take biopsies of normal-looking areas of the bowel.  Results from these tests will then determine the future treatment.

What are the risks?

A colonoscopy has small but definite risks*.  The risk of perforating the bowel is about one in 1,200, of significant bleeding about one in 600, and of death about one in 14,000.  I have not yet caused a perforation or a death, but the risk does exist.  The test is extremely accurate and the best investigation to evaluate the colon, but it is possible to miss a small polyp, especially if the colon is not completely clean after the bowel preparation. 

Most people have windy cramps for an hour or two afterwards.  Your bowel actions will take a day or two to return to normal.  After you have had sedation someone else should drive you home.