Two days before your appointment, you will start your preparation with a change in diet and taking medication. One of the medications is designed to clean out your bowel, and so you will experience the need for the toilet with some diarrhoea. The other medication is a liquid used to coat the bowel, which is seen on the CT imaging. 

On the day of your appointment, please attend the Imaging Department 15 minutes before your examination. You will be invited into the CT Scanning area with a Senior Radiographer and Consultant Radiologist who will be undertaking your colonography procedure. We will ask you to remove all clothing, store them in a changing cubicle and wear a hospital gown to maintain dignity. There are also toilet facilities inside the changing cubicle. 

You will be asked to lie down on the CT scanning table. The radiographer will give you an overview of the examination and place a cannula (typically) into a vein in your elbow or wrist. We may inject an Antispasmodic medication (Buscopan) through the cannula to help reduce the frequency and intensity of the cramping associated with the insufflation of the bowel. 

The Radiologist will ask you to lie on your side and bring your knees into your chest. They will then place a small tube into the ‘back passage’ (rectum). The tube is smaller than a biro pen and is inserted approximately 1.5cm with a balloon to hold it in place. This may cause you some discomfort or a feeling of urgently needing the toilet, but please rest assured that the balloon will prevent any soiling. 

You may feel odd sensations such as ‘gurgling’ or cramping of the abdomen; these may be uncomfortable but are generally tolerated by most patients. The CT scanner uses a controlled amount of X-rays to produce three-dimensional images of all the vital organs and, in particular for this examination, of the bowel. The scanner will ask for several 5-second breath holds and an injection of iodinated contrast will be administered through your cannula under the observation of the Radiographer: this typically causes the sensations of a hot flush all over your body, a metallic taste or smell, and a feeling of passing water (likened to sitting in a heated car seat), these pass within a few minutes, after which the Radiographer or Radiologist will remove the tube from the back passage and the cannula. 

We will support you throughout this procedure, and the insufflation will take around 10 minutes, after which you may privately use the toilet facilities – the gas used is Carbon Dioxide and can be expelled as flatulence or reabsorbed by your body as part of the respiration process.

Two days before the appointment 

• Please eat a low-fibre diet. For more information about what to eat, please refer to the section ‘What is a low-fibre diet?’
• Throughout the day, please drink plenty of fluids, such as tea, coffee, water, fizzy drinks and clear fruit juices (apple, grape, cranberry) to keep hydrated. 
• In the evening, please take the Dulcolax tablets with food. 

One day before the appointment 

• At breakfast, please eat a low-fibre meal and drink 30ml of Gastrograffin (measuring this out using the cup provided; this can be diluted with squash or water). 
• At lunch, please eat a low-fibre meal and drink 30ml of Gastrograffin. 
• For the rest of the day, please just eat foods from the list below: 
  • Clear soups 
  • Jelly 
  • Ice cream 
  • Custard 
  • Complan 
  • Bovril 
  • Oxo drinks 
  • Clear juices 
  • Tea/Coffee 
  • Water  
• In the evening, please drink 30ml of Gastrograffin. There will be 10ml of Gastromiro left in the bottle – please discard this. If the additional 10ml is accidentally ingested, please rest assured that there is no cause for concern. 
• Throughout all days of preparation, please drink plenty of fluids, such as tea, coffee, water, fizzy drinks and clear fruit juices (apple, grape, cranberry) to keep hydrated.   

Please note that the Gastrograffin must be used within 72 hours once opened. 

The day of the appointment

Please do not eat any food, but do keep hydrated throughout the day by drinking plenty of still water, squash, tea/coffee (without milk).

You may experience abdominal cramp-like pains over the next few hours; the air administered during the procedure will be absorbed over the next few hours. Keep hydrated to assist in flushing the iodinated contrast from your body – it will be excreted in your urine and make no changes in colour or smell etc.

You may experience some diarrhoea after the procedure.

The muscle relaxant injection may blur your eyesight over the next few hours. You should not drive or operate machinery until your eyesight returns to normal. Very rarely, in people who are at risk of glaucoma, the injection can cause a very red eye. If this happens, you should call your GP as an emergency.

If you have any concerns following the procedure, please call the Imaging Department on 020 8949 9031 between 8:00 and 20:00.

If your call is out of these hours, please call the Nurse in Charge on 020 8949 9000.