Having a CT colonography

Understanding CT Colonography

This leaflet has been prepared to help you understand the procedure. It includes answers to questions patients often ask. Please read it carefully.

If you have any other questions, please discuss them with the radiographer or your own doctor before the examination.

What is CT Colonography?

It is an X-Ray examination of your colon (large bowel). A small catheter is put into your back passage and gas (CO2) is passed through this into your bowel. This swells your bowel to allow it to be shown on the CT images.

What can be expected during CT Colonography?

CT Colonography is usually well tolerated. There is often a feeling of pressure, bloating, or cramping during the procedure.

You may also have an injection of a contrast agent to highlight parts of your body. This will depend on your medical history. The radiographer will check if there are any reasons why you should not have this.

How do I prepare for this?

The colon must be clean for the procedure to be accurate and complete. The CT Department has given you detailed instructions about dietary restrictions and the cleansing or tagging routine to be used.

What about my current medicines?

You may take most medicines as usual.

Iron tablets can interfere with the preparation for the examination. You must stop taking these 1 week before. You can take them again the day after.

Who will be doing it?

A radiographer will do the examination. He or she will be working with a consultant radiologist (specialist doctor).

The consultant radiologist and radiographer will review and interpret the images. They will send a report on the interpretation to the doctor who referred you.

What is the specialist looking for?

The images of the bowel will allow them to spot any abnormal areas caused by inflammation, narrowing of the bowel, or growths within the bowel.

The specialist will also be looking for growths from the lining of the bowel called polyps. These are found in many people and can become cancerous. Depending on the size of the polyps, the specialist may recommend you have a colonoscopy. This can show the lining directly and remove the polyps where necessary. The benefit of CT colonography is that, should any polyps be seen, the position and size of the polyps within the bowel can be identified. This is helpful information if colonoscopy is required.

What happens after?

You may have some cramping or bloating because of the air passed into the colon. This should disappear quickly as you pass gas. You may feel a little uncomfortable and thus unable to drive. We suggest you arrange transport home but there is no medical reason why you cannot drive.

You may eat and drink normally straight away. You should start taking any medicines that you stopped to prepare for the test.

Special instructions for diabetic medicine are included on the dietary information sheet.

Where do I get my results?

• The results are sent to the doctor who referred you.
• If this was your GP, check with your practice in 2-3 weeks
• If it was a hospital consultant, he or she will either arrange to see you or will write to your GP

CT Colonography is generally safe. Possible complication include:

• a perforation or tear through the bowel wall that could need surgery. This is very uncommon bleeding due to the position of the catheter in the back passage. It is usually minor and stops on its own 
• another risk is that the test will miss a significant bowel problem such as cancer. This risk is kept to a minimum by using the most up to date methods, and constantly measuring the accuracy of our tests

Although they are not common, it is important for you to recognise early signs of any possible complications.