An illustration of a man lying on his side with a doctor looking at a screen. The man has a tube with a camera n his back passage which is looking at his bowel. his bowel
Image courtesy of CRUK/Wikimedia Commons

A colonoscopy is an examination of your large bowel. The doctor does the examination by putting a thin flexible tube with a small camera and light on it (colonscope) into your back passage and along your bowel. 

It is a day procedure (you do not need to stay in hospital overnight).

Before the test

You have to clear your bowel before the test. You will be given a medicine to drink regularly before the test to clear out your bowels. You will also have to fast (not eat) and not drink for a time before the test. The hospital will give you information on exactly what to do.

Will I have pain relief / anaesthetic?

You may have a sedative just before the test to help you relax.

During the test

You will lie on your side and your doctor will put the colonoscope (thin flexible tube) into your back passage. A light inside the tube helps your doctor to see any abnormal areas or swellings. Photos and samples of your bowel can be taken.

How long does it take?

About 1 hour.

Does it hurt?

It may be a little uncomfortable having the tube in your back passage.

After the test

Once the sedation wears off (about an hour), you can go home. Make sure you arrange for someone to take you home as you’re not allowed to drive for 24 hours after a sedative.

CT colonography – virtual colonoscopy

In some hospitals you may be offered a CT colonoscopy. This builds up a detailed picture of the tissues inside your bowel.

Before the test

Your bowels will need to be fully cleared beforehand with laxative tablets and fluids.

During the test

Your doctor puts a tube into your back passage and pumps in air or carbon dioxide to give a clearer picture. Then two CT scans are taken: one while you are lying on your back and the other on your front. You may be asked to hold your breath during the scan. The computer then matches up the two scans to make a 3D picture of your bowel. This is a ‘virtual’ picture.

Colonoscopy video

Cancer Research UK has a very helpful video on this.

For more information

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