Computer Tomography (CT) Colonography

Your doctor has advised you have a Computed Tomography (CT) colonography to help find the cause of your symptoms or as part of a routine screening programme to detect (find) disease or abnormalities (unusual areas) at an early stage in people with no symptoms.

This leaflet tells you about CT colonography. It will also help you to understand what will happen during and after your examination.

What is a CT Colonogrpahy?

A CT colonography is an X-ray examination, also known as a virtual colonoscopy. It is a type of body scan, which looks at the large intestine (bowel or colon). This can be carried out instead of a colonoscopy or barium enema.

Who will perform the test?

A specialist Radiographer (someone trained to take the scans) will carry out the examination and a Radiologist (a Doctor who specialises in X-rays, ultrasound and other similar types of examinations and reports on the findings) may be present.

What are the risks and possible complications?

• Radiation: CT scans involve the use of radiation. Radiation risks from X-rays are small with the dosages used in this examination. The benefits of this examination outweigh any small radiation risk.
  -If you think you may be pregnant, you must let staff know as soon as possible before the examination.

• Discomfort: You may feel some discomfort during the procedure; we try to keep this to a minimum. You can ask for the procedure to stop at any point if you wish.

• Bloating: You may feel bloated for a few hours afterwards. 

• Perforation (hole): One patient in every 700 can suffer a perforation in the wall of the bowel¹. If this happens, treatment may be needed.

What will I need to do to prepare for my procedure?

It is very important that your bowel is empty and clean so that all areas of your bowel can be seen.

You must follow the instructions given in this leaflet.

Please read the back of the bottle and contact the specialist radiographers in the X-ray Department for further advice if you answer yes to any of the following questions (see contact numbers).

• Are you allergic to any of the ingredients listed on the bottle?

• Are you pregnant or breastfeeding?

• Do you suffer from any kidney disease?

You will be asked to drink a liquid called Gastrograffin, which can have an effect on your bowel movements, making them more frequent than usual.

What is Gastrograffin Liquid?

Gastrograffin contains iodine, which is commonly used in Radiology. The liquid may have a slight laxative effect. Do not worry if you find this is not the case for you. If you have any worries or concerns, please contact the X-ray Department for advice (see contact numbers).

If you have had an allergic reaction to iodine in the past, please contact the department to discuss this. We may need to give you a different preparation.

3 days before your appointment

Stop taking any drugs that may cause you to become constipated, for example, Lomotil, codeine phosphate, fybrogel or iron tablets, but continue to take all other usual medications.

The day before your appointment

You must follow a low residue / low fibre diet. This includes white bread, rice, pasta and eggs, cheese and meat. Vegan alternatives are also acceptable.

The table below shows a suggested menu for the day. You can vary from this list, as long as the food consumed is low in fibre. However, please ensure the gastrograffin liquid are consumed at the times specified.

Diet list

No further solid food, milk or dairy products until after the procedure

Information for Diabetic Patients

• Ideally, you will be given an early morning appointment.

• If you take insulin, please phone your diabetic liaison nurse (hospital or GP) for advice.

• Bring something to eat with you for after the test.

• If you are on a combination of long acting and short acting insulin injections, please contact us. We will need to ensure you have an early appointment.

• Insulin pumps will need to be removed before entering the scan room.

As you are at a risk of having a hypoglycaemic episode or ‘hypo’ (low blood sugar), it is important you test your blood sugar regularly.  As the preparation section states, you are allowed to drink fluids such as Lucozade^®, fizzy drinks and fruit juice (no bits) at any time.

Symptoms of a ‘hypo’ are sweating, shakiness, blurred vision, dizziness and confusion.

The day before the CT (Diabetic Patients)

• Take your usual insulin/diabetic tablets with your breakfast.

• Follow dietary instructions all day.

• When you are having fluids only: Reduce insulin doses by half and continue diabetic tablets as normal.

• Check your blood sugar regularly.

• If your blood sugar is below 5, drink sugary drinks to avoid having a ‘hypo’.

The day of the CT (Diabetic Patients)

• Continue to have sugary fluids up until your scan.

• Before you are due to have your scan, test your blood sugar, if possible.

• Bring your insulin/tablets with you and a light meal/sandwich with you to have after the test.

• Do not take any more insulin/tablets until after the scan.

In the rare case that you have an afternoon appointment, you should take your usual dose of insulin in the morning only. Do not take diabetic tablets.

What will happen when I arrive for my appointment?

You will be sent a letter asking you to attend the CT Department, which is in the main X-ray Department.

Before your examination, you will be taken to a private area. You will be given a hospital gown to put on and you will be asked to remove all of your clothing below the waist.

What will happen during my examination?

The Radiographer will discuss the procedure with you and complete a health questionnaire.

You will be asked to lie down on the CT table on your left side, with your knees slightly bent.

A soft tube will then be gently inserted into your rectum (back passage). Carbon dioxide will be passed through the tube to inflate your bowel so that your Radiologist can see all parts of your bowel wall.

This is done using an electronic pump so that the pressure inside your bowel is safely controlled. This can cause ‘windy’ discomfort for a short time.

Once the bowel is fully inflated, a CT scan is carried out. The examination can take up to 20 minutes to complete. Any symptoms will quickly pass when the tube is removed and you go to the toilet.

Usually, two scans are taken in different positions, the first with you lying on your back and the other on your tummy or side. You will need to keep still during this time. Sometimes a third scan may be needed if the radiologist needs more information.

Sometimes, an injection of contrast medium dye may be needed. If this is needed, your Radiographer will insert a cannula (fine needle) in the back of your hand or arm, so that we can inject the contrast medium. This injection usually causes nothing more than a warm sensation passing through your body.

Will it be painful?

The Radiographer will give you a muscle relaxant known as Buscopan. This will depend on your health condition.

This can make your mouth dry and sometimes cause blurred vision. This usually lasts 15 – 20 minutes.

If you develop pain or redness of your eyes within 24 hours of having this test, you should contact the Accident and Emergency Department at your local hospital for advice. It is rare for this to happen.

You can ask for the procedure to stop at any point if you wish.

What will happen after my examination?

After your examination has finished, you can go home and you will be able to eat and drink as normal.

How will I get my results?

You will not be told any results of the test on the day. If your GP requested the scan, the results will be sent to them. If a hospital Consultant has sent you for the scan, you will be invited to attend a follow-up appointment to discuss the results.

Contact

University Hospital of North Tees and Hartlepool Foundation Trust

X-Ray Department
Monday to Friday 09:00am -05:00pm
Telephone: 01642 624842

Diabetes Specialist Nurse
Monday to Friday 09:00am -05:00pm
University Hospital of North Tees: 01642 624519
University Hospital of Hartlepool: 01429 522594

Emergency Department
24 hours a day, 7 days a week
Telephone: 01642 382899

Further information

1. The patient.co.uk website has more detailed information about CT colonography: www.patient.co.uk/health/CT-Colonography.htm
2. https://www.radiologyinfo.org/en/info.cfm?pg=ct_colo, accessed 12/04/17

References

1. Bellini, D., Rengo, M., De Cecco, C.N., Iafrate, F., Hassan, C. and Laghi, A, 2014. Perforation rate in CT colonography: a systematic review of the literature and meta-analysis. European radiology, 24(7), pp.1487-1496.

PIL number: PIL1320
Date for review:11/08/2024

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