If you come for a colonoscopy at Great Ormond Street Hospital (GOSH) it will be so a doctor can look inside your large intestine.

The digestive system

Your digestive system is made up of your food pipe, stomach, small and large intestines, rectum and anus. When you eat something, the food travels down your food pipe and into your stomach, where it’s turned into a mushy liquid.

From there, it travels through the small and large intestines, where all the goodness and excess water is taken out. Finally it travels to the rectum, from where it comes out through your anus when you go to the toilet.

Why you might need a colonoscopy

A colonoscopy is a test that lets the doctor look inside your large intestine, using a long, bendy tube with a built-in camera and a light. Colonoscopies are used to diagnose conditions affecting the large intestine.

Colonoscopies are usually used to diagnose problems with the large intestine, such as not absorbing enough goodness from food, problems with pooing or bleeding. It is a good way of finding out more about a person’s problem, without an operation.

It’s really important that the intestine is empty for a colonoscopy, so the doctor can see everything inside it. Someone having a colonoscopy will have to stop eating and drinking for a few hours beforehand, and will also need to take some medicine to empty their intestines completely.

What happens

Most colonoscopies are done while the person is sedated, so that they are more relaxed and the test can be done more quickly. The endoscope (a long, bendy tube with a built-in camera and light) is inserted into the anus and passed up through the intestine.

The doctor can take biopsies (small samples of tissue) from the intestine during this test, which can then be examined under a microscope. Most people can go home straightaway after the colonoscopy and start eating and drinking normally.

Last reviewed: February 2011

Compiled by:
Great Ormond Street Hospital