Advice after your nerve block for surgery
On this page…
Introduction
We have given you this factsheet because you have an appointment for a CT scan following oral contrast. Please make sure you read this information and follow the instructions carefully before your procedure. If you have any further questions, please speak to a member of your healthcare team who will be pleased to advise you.
The procedure involves a computerised tomography (CT) scanner taking images of your abdomen and pelvis. These images are cross-sectional (like slices) and are used to produce 2D and 3D images of the large bowel (colon) to look for polyps or tumours.
This leaflet may not answer all your questions and it is not meant to replace informed discussion between you and your doctor, but can act as a starting point for such discussions.
If you have any questions about the procedure, please ask the doctor who has referred you or the department that will be performing it.
Are there alternatives to CT?
Colonoscopy is an alternative way of examining the large bowel. In this, a thin tube with a camera on the end (colonoscope) is passed into the back passage and moved up and around the bowel. The procedure is more invasive than CT and usually requires sedation.
However, it does allow a biopsy (tissue removed for testing) or polyp removal if needed.
Colonoscopy will only examine the inside of the large bowel. CT also provides some
information about other organs and structures inside the abdomen.
Preparation for the procedure
To give us a clear view, you must take a ‘tagging’ liquid called Gastrograffin. Gastrografin is an iodine based liquid which acts as a dye to help us distinguish stool from polyps.
You will need to follow instructions regarding the Gastrografin, and your diet, or the test may fail and may need repeating. These instructions are at the end of this booklet.
You will need to:
- drink the Gastrografin we have provided.
- follow a low fibre and low fat diet.
Gastrografin may cause loose bowel movements, so it is important that you drink plenty of fluids to avoid becoming dehydrated. Please make sure you have access to and are near a toilet once you have started taking your bowel preparation.
Before your appointment (and before taking the Gastrografin)
Please let us know if:
- you suffer with an allergy to iodine.
- you have limited mobility and will require assistance to get on and off the scanner.
- you will need an interpreter. We are not able to use family members or friends to interpret.
- there is any possibility that you may be pregnant.
In order to make your appointment run more smoothly, please let us know if any of these apply, in advance, by calling our bookings team (contact details are displayed on the main Radiology page).
On Arrival
Please arrive 15 minutes before your appointment time.
On arrival in the department you should check in at the reception desk. Bring this letter with you and be prepared to confirm your details with the receptionist. All patients from 12-55 years of age (regardless of gender) who will undergo a Radiology procedure will be asked about the possibility of them being pregnant.
During the procedure
- A Radiographer or Health Care Professional will call you from the waiting room for your CT scan. As other patients are having different scans and tests whilst you wait, you may note other patients being called out of order of arrival.
- Your scan may need some preparation beforehand. You may be asked to change into a hospital gown and remove jewellery (this may be best left at home, as the Trust cannot accept responsibility for lost or stolen items).
- We will ask you a series of questions to make sure the scan is safe and can then go ahead.
- A small needle (cannula) may be placed into your arm, in preparation for your scan.
- When you are ready a Radiographer will call you through into the scan room and ask you to lie down on the CT scanner bed and the scan will occur.
- The CT scanner looks like a large doughnut and the scan bed moves in and out of the middle in order to obtain your scan. The CT scanner is not enclosed, so claustrophobia is not normally an issue. There may be breathing instructions for you to follow; these may require you to hold your breath for up to 10 seconds. If you struggle to hold your breath for this long or find it difficult lying flat on your back, then let the Radiographers know when you arrive.
- The radiographers will be in the CT control room but you will be able to talk to them via an intercom, and they will be watching you all the time.
- We may give you a muscle relaxant (Buscopan) via the cannula to prevent bowel spasm. This may give you a dry mouth and blurred vision for about 20 minutes.
- We will take CT scan pictures of you lying on your back, your front and/or your side.
Sometimes we may take CT scan pictures of your chest to complete the examination. - We will usually give you an infusion of x-ray contrast (dye) through the cannula in your arm. A short, hot flush and feeling like you are passing urine (weeing) are common side effects of this contrast.
- We will ask you to hold your breath for about ten seconds each time we take scan pictures.
- We will remove the cannula.
- The procedure takes around 20 minutes, but please expect to be with us for an hour or so in total.
After the procedure
We will ask you to wait in the department for a short time after the procedure. This is to make sure that you feel well and any abdominal discomfort is getting better before you go home.
You may experience some further diarrhoea for the rest of the day. We recommend that you stay close to a toilet. You can eat normally after the procedure and you should drink plenty of fluids.
Results
You will not receive the results of the investigation immediately as the images need to be carefully analysed. A specialist doctor (radiologist) or radiographer will write a report and this will be sent to your consultant or specialist screening practitioner. This can take up to 4 weeks.
Risks
- There is exposure to X-ray radiation during the procedure. However, the amount of radiation you will receive is kept to as low as reasonably possible.
- Some people may have a rare allergic reaction to the x-ray contrast. We will go through a safety checklist before the procedure to identify if you are at increased risk. A hot flush, feeling of passing urine and metallic taste are common side effects of the x-ray contrast.
- No test is always 100% accurate and both CT colonography and colonoscopy can miss bowel tumours
Other side effects that may occur include:
- Painful, blurred vision of one or both of your eyes. This is a rare side effect from the muscle relaxant (Buscopan). If you experience this, you must attend hospital immediately.
- Abdominal discomfort. This should get better as you move around and start to eat.
- Dehydration. You should drink more fluids particularly during the bowel preparation.
- A sore bottom from loose stools.
If you have diabetes
If you are diabetic and need additional advice on how to manage your diabetic medication during the two days of preparation, please contact your diabetic nurse specialist or GP surgery for specific instructions.
Diet Instructions before your test
|
Day |
Time |
Diet, Drink, Medication |
Completed Check |
|
7 Days before day of procedure |
|
Stop any Iron supplements. Continue other medication |
|
|
4 days before procedure |
|
Stop any constipating medication such as Loperamide. Continue other medication |
|
|
1 day before procedure |
Drink plenty of fluids
|
||
|
7am-9am |
Breakfast from the ‘low residue’ list
|
|
|
|
Clear Fluids only from now on – see below
|
|||
|
9-10am |
Drink First bottle of Gastrograffin 50ml. This can be mixed with 50ml water and squash to taste |
|
|
|
12 midday |
Small light lunch from the ‘low residue’ list
|
|
|
|
No more solid foods, milk or dairy products. Continue with clear fluids only
|
|||
|
5-6pm |
Drink second bottle of Gastrograffin 50ml. This can be mixed with 50ml water and squash to taste |
|
|
|
Day of procedure |
No solid foods, milk or dairy products. Continue with clear fluids
|
||
|
After Procedure |
Eat and Drink as normal
|
||
Low Residue food examples
Eggs: Boiled, Poached
Cereal: Crisped rice cereal, corn flakes. No Bran or high fibre
Cheese: Cream cheese, cottage cheese, cheese sauce
Potatoes (no skin): Boiled, mashed, baked
Rice: plain boiled white rice
Pasta or noodles: White
Meat/Fish: lean beef,lamb, ham, pork, veal, poultry, fish
Bread: White
Desert: clear jelly
Clear Fluids: Water, energy drinks, soda water, black tea/coffee, squashes, strained fruit juice, clear soups or drinks made from stock/meat extract cubes
Contact us
If you have any queries relating to this information, please contact the Radiology service.
About this information
Service:
Radiology
Reference:
PILS-CT.11
Approval date:
2 October 2024
Review date:
2 October 2027
Click ‘show accessibility tools’ at the bottom of the page
Then click ‘select language’
Alternative formats
You can use the accessibility toolbar at the bottom of your screen to:
-
Change the text size
-
Adjust the font
-
Modify the colour contrast
-
Use the translate function
If you would like this information in another format, such as Braille, audio, or easy read, please speak to a member of staff.
You can also print as well as download as PDF using the “Print this page” button at the end of the page.
Staff will print a copy for you on request
Important note
This page provides general information only. It is developed by clinical staff and is reviewed regularly every 3 years for accuracy. For personal advice about your health, or if you have any concerns, please speak to your doctor.