What is computed tomography colonography (CTC)?
Computed tomography colonography is a CT scan that looks at the large bowel (colon) and abdomen. It is used as an alternative to a Colonoscopy. A trained member of staff will place a thin tube into your rectum. Gas is then put into your colon through the tube to distend (expand) your colon. A CT scan is then performed to take pictures of your bowel.
You will normally be in the scan room for no longer than 30 minutes, and the scan itself usually takes around 10 minutes.
Who will perform the test?
A specially trained radiographer will carry out the examination.
How do I prepare for the test?
You will need to drink the Omnipaque liquid to prepare for the test. This is to help us see your colon and its contents clearly. A special diet is very important before the test (low residue) along with the bowel preparation (Omnipaque liquid). You will need to start the preparation 2 days before your appointment. Once you have taken the preparation, it is important to be as close to a toilet as it often causes frequent loose bowel motions. If you take iron tablets please stop taking these three days before your appointment.
Bowel preparation for CT colonography
A special diet has been designed to prepare and cleanse your colon before your examination.
It is important to follow this diet properly because too much
faeces in your bowel can make it difficult for the doctor looking at the scan.
Omnipaque liquid (bowel preparation)
Although this liquid does have a slight laxative effect, it is designed to allow us to clearly see faeces in your colon. Do not be alarmed if you haven’t been to the toilet many times after drinking the liquid, your test can still be performed. Omnipaque is safe to drink. If you have had a severe allergic reaction to x-ray contrast in the past we may need to give you an alternative preparation. Please telephone us for further advice if you think you may have an allergy.
Females of child bearing age
If you suspect you might be pregnant you must contact the radiology department in advance to rearrange your appointment. If you are taking the oral contraceptive pill, diarrhoea can make it less effective. Continue taking the pill but use other precautions for the rest of that cycle.
Special information for people with diabetes
If you have diabetes please ensure that you discuss this procedure with your diabetes nurse specialist at your GP surgery or in hospital.
Preparation for CT Colonography
This preparation is designed to prepare the bowel prior to the examination. It may result in extra bowel movements after the first dose so it is advisable that you have access to a toilet.
2 days before the CT examination
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Step 1 |
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Breakfast Tea/coffee, no milk Choose from the following: clear soup (eg. strained chicken noodle soup, vegetable bouillon), jelly, ice cream, custard, complan drinks, Bovril and oxo drinks, clear juices, fizzy drinks.
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Mid-morning Drink clear liquid such as water, fruit cordials, herbal tea, Bovril or fizzy soft drinks. |
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Lunch/Dinner Choose from the list given for breakfast
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6pm: Drink 50mls from first bottle of Omnipaque with 50mls water. This may be diluted with cordial. |
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Step 2 |
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Breakfast Tea/coffee, no milk Choose from the following: clear soup (eg. strained chicken noodle soup, vegetable bouillon), jelly, ice cream, custard, complan drinks, Bovril and oxo drinks, clear juices, fizzy drinks.
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10 am: Drink from remainder of first bottle of Omnipaque with 50mls water. This may be diluted with cordial. |
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Lunch/Dinner Choose from the list given for breakfast
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6 pm: Drink 50mls from second bottle of Omnipaque with 50mls water. This may be diluted with cordial. |
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Step 3 |
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On the morning of your scan DO NOT EAT ANY SOLID FOOD. You may drink water or clear sugary drinks. |
If you take any regular medications please bring a list of them with you
What happens before, during and after the test?
When you arrive in the department
You will be asked to change into a hospital gown on your arrival. We will ask you some questions and explain the procedure to you so that you understand what is happening. You can also
ask us questions at any time if you are unsure about what is happening. We will also get you to sign to give your consent for the procedure. This states that you agree to have the treatment and you understand what it involves. A member of staff will put a needle (cannula) into a vein in your arm before you enter the scan room. This is so that a muscle relaxant (Buscopan) and possibly x-ray contrast medium can be injected during the scan. The scan takes about 10 to 30 minutes but you will be in the department for about one hour. We will try to keep to your appointment time but occasionally we have to scan patients urgently at short notice. This means that your appointment could be delayed – we will let you know if this is the case
During the test:
You will be taken into the CT scan room, asked to lie on the table on your left side. A small soft tube is inserted into your rectum (back passage) and your colon is filled with gas (carbon dioxide) using a special machine at a controlled rate. When the carbon dioxide is being introduced you may get some bloating, mild discomfort in your abdomen like ‘bad wind’ and the sensation you need to go to the toilet. The injection of Buscopan should help to ease these symptoms
Once the radiographer is satisfied with the amount of gas two scans are then performed. The first position is with you lying on your tummy or on your left side, and a second position with you lying on your back. For the scan the table will move you in and out of the CT scanner and ask you to hold your breath for a few seconds. A third scan may be needed so that we can see the whole of the large bowel clearly. Occasionally we may need to give you an injection of x-ray dye to give more information of other organs on the scan pictures.
After the test
After the scan has been completed the tube will be removed from your back passage. You will then be taken to the toilet to expel as much of the gas as you can and get dressed. We ask you to stay in the department for around 30 minutes after the test to make sure you feel all right. During this time you will be offered a hot drink and something to eat.
What to do when you leave the department
You can go back to eating and drinking as normal, and resume you normal daily activities. You should be aware that the Omnipaque may still have a slight laxative effect after the test. Please contact your GP or go to your nearest A&E if you feel unwell.
Are there side-effects or risks from the procedure?
CT scanning involves x-rays. The amount of radiation used is more than an ordinary x-ray of the chest or body and is equal to the natural radiation we receive from the atmosphere over a period of approximately three years. The risk from this radiation dose is very low. Mild abdominal discomfort and bloating can occur when gas goes into the colon. We use carbon dioxide gas because the body quickly absorbs it. Any symptoms quickly pass off when the tubing is removed from the rectum and you have gone to the toilet. Any residual carbon dioxide will be absorbed by your body and you will breathe this out.
Buscopan (muscle relaxant) can make your mouth dry, your vision slightly blurred and occasionally some heart palpitations, which normally lasts for 15-20 minutes. Very rarely patients may develop pain or redness of the eyes which occurs in the 24 hours after the test. If this happens, you should go to an Accident & Emergency department immediately for a check-up. Please remember that this eye problem is very rare (it has not happened in any of our patients having a CT colonography so far).
If you suffer from either a condition called Myasthenia Gravis or a condition called Porphyria please inform the radiographers when you enter the scan room for your examination.
If you have any heart problems such as angina, Cardiac arrhythmia or if you have had a recent heart attack then inform the radiographers when you attend for the test as you may not be suitable for the injection of Buscopan. If you use a GTN spray for angina please bring this with you when you attend for your test.
Perforation of the bowel can occur with this test but this is also very rare (approx 1 in 3000 tests). When it happens nearly all cases resolve without treatment, but it may require hospital admission and observation under the care of a surgeon in case an operation is needed.
Despite these small risks, your doctor believes it is advisable that you should have this examination. Do bear in mind that there are greater risks from missing a serious condition like bowel cancer by not having it. Please remember this test is safe - serious complications are rare.
How do I get my results?
You will not get any results on the day of you scan. The pictures taken during the scan will be carefully looked at by a radiologist, who will produce a detailed report. The report will be sent to the doctor who referred you for the scan. They should then get in contact with you to discuss the results and any further treatment you may need.
If you have any further queries or questions please contact the department on 01228 814587
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Feedback
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