Virtual colonoscopy

Virtual colonoscopy is a newer test that is also called computerised tomography colonography (CTC). You may have to travel to a specialist centre if you need it. Your doctor or nurse can give you more information about it.

A computer uses CT scanning images to examine your bowel. A CT scan takes a series of x-rays, which builds up a three-dimensional picture of the inside of the body. The CT scan uses a small amount of radiation, which is very unlikely to harm you and won’t harm anyone you come into contact with.

The preparation is similar to having a colonoscopy. You’ll be asked to drink fluids and take a laxative about a day before the scan. Virtual colonoscopy takes place in the hospital CT scanning department and you can usually have it done as an outpatient.

Just before the CT scan, the doctor passes a tube into your back passage (rectum) and pumps in some air and gas (carbon dioxide). This expands the bowel and helps to give a clearer picture. You may also be given an injection of a dye, which allows areas of the bowel to be seen more clearly. This may make you feel hot all over for a few minutes.

It’s important to let your doctor know if you’re allergic to iodine or have asthma, because you could have a more serious reaction to the injection.

You may be given a drug called hyoscine (Buscopan®) to relax the muscle of the bowel. This may make your vision blurred for a short time. It’s important to tell the doctor if you have glaucoma, because this drug can make it worse.

You’ll have two CT scans – one lying on your back and one on your front. The computer matches up the two scans to create a virtual image of the inside of your bowel.

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, your family or a close friend. Your specialist nurse 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.