Virtual colonoscopy

This test uses a CT scanner to create a picture of the bowel.

In a virtual colonoscopy, a CT scanner takes a series of x-rays, which builds up a three-dimensional picture of your bowel. It is done in the hospital CT department. You can usually have it as an outpatient.

This test may be done instead of a colonoscopy, or it may be done if the colonoscopy did not give a clear enough picture.

You will need to follow a special diet for a few days. You will also be given a liquid to drink, called gastrografin. The liquid works like a laxative to help clear out your bowel. It also helps show poo still in the bowel on the scan picture. Your hospital will give you instructions of how and when to take the gastrografin.

Your doctor may give you an injection to help the muscles in the bowel relax. You may also have an injection of a dye (contrast) at the same time. Your doctor will tell you if you are going to have this.

Just before the scan, your doctor passes a tube into the back passage (rectum) and pumps in some air and gas (carbon dioxide).

This expands the bowel and helps give a clearer picture. You will have two CT scans – one lying on your back and one lying on your front.

Waiting for test results

Waiting for test results can be a difficult time. It may take from a few days to a couple of weeks for the results of your tests to be ready. You may find it helpful to talk with your partner, family or a close friend. Your specialist nurse or one of the organisations listed on our database, can also provide support. You can also talk things over with one of our cancer support specialists on 0808 808 00 00.

Back to Bowel screening

The FOB and FIT tests

These tests check for tiny amounts of blood in poo, which can be a sign of polyps or bowel cancer.

Bowel scope screening

This test looks at the lower part of your large bowel. It can help find cancer at an early stage.


A colonoscopy is a test that looks at the inside of the large bowel.

Be bowel aware

It is good to be aware of the symptoms of bowel cancer and ways to reduce your risk.