Having a CT Colonography (CTC) Scan with Picolax
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 especially trained in CTC in conjunction with a radiologist and usually lasts for no longer than 30 minutes, although you may be in the department for up to an hour.
There will be another trained member of staff or radiography department assistant in the room during the procedure. You will be asked to change into a hospital gown when you arrive in the department which will be provided for you. You may bring your own dressing gown to wear on top if you wish.
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 dye (iodine-based) during the scan.
A member of staff will take you into the scan room, ask you some questions and explain the procedure so that you understand what is happening. You can ask us any questions you may have at any time.
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.
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 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 (which limits dietary fibre and other foods that might stimulate bowel activity) for a couple of days before the test and take a mild laxative and a liquid called Gastrograffin which you have already collected. Full instructions for the preparation are on the following pages.
Pregnancy status
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 its effectiveness, so 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 the team on 01305 255397.
About this leaflet
Author: Simon Jones, Lead Radiographer CT
and Dr Kathy Lawrence, Consultant Radiologist
Written: August 2018
Updated and approved: July 2022
Review date: July 2025
Edition: v3
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