CT Colonography with Picolax Only

What is CT Colonography and how is it performed?

Computerised tomography (CT) is a scan that uses x-rays to look at organs within the body. CT Colonography (CTC) is designed to look at the large bowel (colon) and abdomen. It is performed as an alternative test to a barium enema or colonoscopy. The examination is performed by a senior radiographer or a radiologist and usually lasts for no longer than 30 minutes although you may be in the department for up to an hour.

During the test, gas (carbon dioxide) will be used to inflate the colon via a thin flexible tube placed in your rectum (back passage). This will make you feel bloated and may give you some mild abdominal discomfort which should quickly ease when the test is complete. A CT scan will then be done with you lying on your back and then either on your front or on your side. Occasionally a third position will be required to get all the information required.

Before the test a small tube (cannula) will be inserted into a vein in your arm. This will be used to give you an injection of a medicine to relax the bowel (Buscopan) and may also be used for x-ray contrast (iodine based) during the scan.

Are there any side effects or risks?

CT Colonography is a very safe examination and complications rarely occur.

CT scans involve x-rays; the amount of radiation used is more than an ordinary x-ray of the chest or body but is about the same as an average person receives from the atmosphere over approximately three years. The scanner we have in Dorchester has the latest software to keep the radiation dose to a minimum.

There is a tiny risk of making a very small hole in the bowel known as a perforation. This happens very rarely in 0.005% of cases. If this does happen, most cases resolve without treatment but may require hospital admission for observation.

If we need to give you x-ray dye, it can very rarely cause an allergic reaction which may need medication or even hospital treatment. This occurs in less than 0.04% of patients.

More commonly it causes a metallic taste in the mouth, nausea or a feeling of warmth passing down your body. This usually passes very quickly.

The medicine used to relax your bowel can give you a dry mouth and also make your vision a little blurred. This should resolve within half an hour but you should not drive home until your vision has returned to normal. Very rarely, patients may develop pain and redness of the eyes within 24 hours following Buscopan. If this occurs you should go immediately to the Emergency Department.

Are there any special preparations for this test?

It is very important that the large bowel is empty when this test is performed. You will need to follow a special low residue diet for a couple of days before the test and also take a strong laxative. Full instructions for the preparation are below.

Female patients

If you are or think you may be pregnant please contact the department. If you are taking the oral contraceptive pill the bowel preparation may reduce their effectiveness, continue taking the tablets but use other precautions for the remainder of that cycle.

After the examination

You will be taken to visit the toilet immediately after the scan has finished. The gas (carbon dioxide) is absorbed by the body and any discomfort should quickly wear off. If your vision has been affected by the Buscopan injection you should wait until your vision returns to normal before driving.

The x-ray dye is removed from your body by your kidneys, therefore it is important to keep well hydrated over the subsequent 48 hours after your appointment.

The doctor who sent you for the examination should get the results within 10 days. If you feel unwell after the test or have any questions or concerns, please contact us on 01305 255397.

About this leaflet

Author: Simon Jones, Lead Radiographer CT and Dr Kathy Lawrence, Consultant Radiologist
Written: August 2018
Approved: September 2023
Review date: September 2026
Edition: v3

References
Public Health England (2011) Ionising radiation: dose comparisons. Gov.uk

1. Flicek, K.T.; Hara, A.K.; Silva, A.C.; Wu, Q.; Peter, M.B.; Johnson, C.D. (2010) Reducing the radiation dose
   for CT colonography Using Adaptive Statistical Iterative Reconstruction: A Pilot Study. American Journal of
   Roentgenology. July 195 (1): 126-131
2. Berrington de Gonzales, A.; Pyo Kim, K.; Yee, J. (2010) CT Colonography: perforation rates and potential
   radiation risks. Gastrointestinal Endoscopy Clinics of North America. April 20 (2): 279-291
3. Siddiqi, N.H. (2015) Incidence of adverse reactions to ICM. Medscape.
   http://emedicine.medscape.com/article/422855-overview#a1
4. Drugs.com (2016) Medicines and Healthcare Products Regulatory Agency.
   http://www.drugs.com/uk/buscopan-ampoules-20mg-ml-leaflet.html

If you have feedback regarding the accuracy of the information contained in this leaflet, or if you would like a list of references used to develop this leaflet, please email patientinformation.leaflets@dchft.nhs.uk

Bowel preparation and diet sheet

Please follow these instructions carefully to make sure that your bowel is as empty as possible and to improve the accuracy of this test.

You should have received some laxative (Picolax). If not, please ring 01305 255397.

If you have diabetes, please seek advice from your diabetic team about how to manage the diet.

Four days before

Continue to take any prescribed medicine, but if you are taking iron tablets you should stop taking them.

Two days before

If you are taking any constipating medicines such as Codeine, Kaolin and Morphine, Loperamide (Imodium), Regulan or Fybogel, stop this two days before you are due to come for the examination. Continue other medications and any laxatives you usually take.

Start low residue diet – you may only eat what is listed below throughout the day.

Foods allowed on low residue diet

• White bread and bread products
• Breakfast cereals such as Cornflakes, Rice Crispies, Special K, Frosties with small amount semi skimmed or skimmed milk
• White pasta, white rice, tapioca, ground rice, semolina
• Peeled potatoes
• Quorn, tofu
• Chicken or turkey
• White fish
• Boiled, poached or scrambled eggs (without cream or butter).
• Boiled sweets, fruit gums, pastilles, plain biscuits e.g. rich tea
• Strained stock, stock cubes, Marmite, Bovril, soy sauce, instant gravy
• Clear fluids including water, fruit squash, rehydration drinks, clear broth, tea/coffee with small amount of milk.

Foods not allowed

• All fruit including dried fruit and vegetables
• Wholemeal, granary, brown and high fibre white breads and bread products
• Potato skins and chips
• Crisps and nuts
• Wholewheat pasta, bran and brown rice
• High fibre breakfast cereals such as Weetabix, Shredded wheat, bran flakes, porridge
• Red meat
• Pulses such as beans and lentils
• Fried or fatty fish
• Full fat milk, cream, full fat yoghurt, ice cream and full fat hard cheese
• Butter and butter like spreads, vegetable oils
• Drinks to avoid are full fat chocolate drinks, drinks with full fat milk, cocoa and vegetable juices.

One day before

Before 8am, take one sachet of Picolax well mixed into a cup of water (approximately 150mls). If the mixture becomes hot, wait until it has cooled sufficiently before drinking. Picolax is a strong laxative and can work quite quickly. You should stay within easy reach of a toilet and ensure you drink plenty of fluids throughout the day to avoid becoming dehydrated. If you are taking other medications, they should be taken two hours before the Picolax or at least six hours afterwards. Allergic reactions are very rare but as with all medications possible.

If you think you are having an allergic reaction seek medical attention, but please note that diarrhoea and irritation of your bottom are not signs of an allergy.

For breakfast you may have:

• Tea/coffee but no milk.

One of the following:

• 2 slices of white bread
• 1boiled/poached egg and 1 slice white bread
• 50g cottage cheese and 1 slice of white bread.

For lunch you may have one of the following:

• 75g white meat/white fish
• 2 boiled/poached eggs
• 100g cheese.

And one of the following:

• 2 slices of white bread
• 2 egg sized potatoes with no skin
• 3 tablespoons plain white pasta or rice.

At 4pm take the second sachet of Picolax prepared as before.

After 4pm, no further solid food, milk or dairy products until after the procedure but drink clear fluids such as fruit cordials, herbal tea, Bovril or fizzy soft drinks. You can also have tea or coffee with no milk.

It is very important that you do not become dehydrated. It is recommended that you try and drink a cup of water/squash or fluid from the allowed foods every hour during the day.

On the day of the scan, you can have clear fluids up to the time of the scan but no solid food. After the scan you can eat and drink as normal and you may want to bring a snack with you to have in the department before going home.