CT Colonography

What is a CT Colonography?

CT is used to create cross sectional pictures of the body. For a colonography, by distending the large bowel (or colon) with carbon dioxide it can be checked for the presence of bowel cancer and benign growths (polyps) that could become cancerous.

This technique can identify up to 95% of large bowel cancers or significant polyps but, like any screening test, is not 100% accurate.

You will be asked to attend our practice a minimum of 3 days prior to your booking to collect an information package containing the specific instructions for your scan. The nursing staff will go through these instructions with you at the time of collection.


The bowel should be prepped correctly so that the bowel is clean before the procedure so that any abnormalities can be detected. The package will contain information, instructions, medications and a diet that must be followed correctly

The procedure takes approximately twenty minutes.

You will be asked to change into a gown and lie on the CT table. A nurse will explain the procedure as you go, and you can ask questions. A small soft tube is placed in the rectum, through which carbon dioxide is passed into your large bowel. This causes it to expand so that the inside wall of the bowel can be clearly seen on the CT images. You will be given a small injection of Buscopan, (muscle relaxant to help this process. As the carbon dioxide passes in, you will feel your abdomen become quite tight and bloated, this is often described as ‘uncomfortable fullness’, and you may feel like burping or passing wind. Occasionally, people may experience mild nausea, which usually passes quickly.


Two scans (usually taking between three (3) to ten (10) seconds) will be taken; one while you are lying on your back and one while you are lying on your front. You will have to hold your breath for this short scan. Occasionally, the scan will be carried out while you lie on your side. The images will be reviewed and once the radiologist is happy, the tube can be removed. You will be able to go to a nearby toilet straight away.

After the test, your abdomen may feel uncomfortable for a few hours, the feeling is often described as bloating or cramping. If this occurs, it usually passes quickly.

You may be hungry or feel a little light-headed from not eating breakfast. The staff can offer you a drink or a sandwich. You may eat as normal afterwards.

If you have had the Buscopan injection to relax the bowel, it is possible, that you may experience blurred vision or a dry mouth. Please let the nurse know as we may monitor you for approximately 30 minutes


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