CT (computerised tomography) colonography is a newer test that is also called virtual colonoscopy.
If you need a CT colonography, you may have to travel to a specialist centre. Your doctor or nurse can give you more information about this test.
Instead of having a colonoscope put into your bowel, 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 , so you’ll be asked to drink fluids and take a laxative a day or so before the scan. CT colonography takes place in the hospital CT scanning department and can usually be 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 can sometimes make you have blurred vision for a short time. It’s very important to tell the doctor if you have glaucoma, as this drug can make it worse.
You’ll have two CT scans - one lying on your back and one on your front. The computer then matches up the two scans to create a virtual image of the inside of your bowel.