Colonoscopy

Why a colonoscopy is done

A colonoscopy is a test to look inside your large bowel (colon and rectum) using a long, thin, flexible tube with a small camera.

It is often used to find the cause of bowel symptoms such as bleeding from the bottom or blood in your poo, diarrhoea or constipation that does not go away, or weight loss or tiredness without a clear reason. It can also find and remove polyps, and help diagnose conditions such as Crohn's disease, ulcerative colitis, diverticular disease and bowel cancer.

For most people the test finds nothing serious.

Preparing for colonoscopy

Your bowel needs to be completely empty so the camera can see clearly. For about 2 days before the test you will usually be asked to eat only plain, low-fibre foods, such as plain chicken or fish, white rice, pasta or bread, and clear soup.

The day before, you drink a strong laxative (bowel preparation) as instructed in your letter. It causes frequent, watery diarrhoea within a few hours, so stay close to a toilet. It is important to take it exactly as instructed, otherwise the test may need to be repeated.

Tell the unit as soon as you receive your appointment if you are pregnant, have diabetes, or take any medicines — especially blood thinners or iron tablets — as some may need to be adjusted or stopped beforehand. If you are having sedation, arrange for someone to take you home.

What happens during the test

You lie on your side on a couch. Depending on the unit, you may be offered a sedative through a small needle in your hand or arm to help you relax, a painkiller, or gas and air.

The colonoscope is passed gently into your bottom and guided around the bowel. Air or gas is used to open the bowel so it can be seen clearly, which can cause bloating, cramps or a feeling that you need the toilet.

Polyps can usually be removed, and small tissue samples (biopsies) taken, during the test. You will not feel this. The test usually takes 30 to 45 minutes.

Results and next steps

The person doing the test can often tell you what they saw before you go home. Results of biopsies or removed polyps take longer — usually 2 to 3 weeks — and are sent by letter or given at a follow-up appointment. Contact the unit if you have not heard after 3 weeks.

If the bowel is normal, you may not need any further tests. If polyps were found, your results will say whether you need treatment or a check-up colonoscopy in the future. If cancer is found, you will be seen by a specialist team as soon as possible. Other conditions, such as inflammatory bowel disease or diverticular disease, will be explained along with their treatment.

Recovery

Bloating and cramps usually pass within 2 to 3 hours. A little bleeding from the bottom for a day or two is common, particularly if polyps were removed or biopsies taken.

If you had sedation, you must not drive, operate machinery or sign important documents for 24 hours, and someone should take you home and ideally stay with you.

Serious problems are rare, but include heavy bleeding, a tear in the bowel, or a reaction to the sedative. Contact the unit, or call NHS 111, straight away if you develop severe tummy pain, heavy bleeding or a high temperature after the test.