What a CT scan is used for
We can conduct a CT scan on any section of the head or body. It can give clear pictures of bones as well as soft tissues. An ordinary x-ray test cannot show things like muscles, organs, large blood vessels and the brain.
A contrast (dye) injection can give more information from the scan. Find out more about CT scans.
When and why we use intravenous contrast
For some CT scans you may need to have an injection of a special dye called intravenous contrast. This helps to show up parts of the body not always clearly seen, like blood vessels, the kidneys and liver.
Your doctor has chosen to use intravenous contrast for your examination after considering the risks and benefit to you. Contrast is a clear fluid usually injected into a vein in the arm immediately before the scan.
Preparing for your CT with contrast examination
It's very important to drink lots of water the day before your appointment and the day after. Pay attention to any specific examination instructions sent to you with your CT appointment letter.
You may need to stop taking certain medicines before the procedure. This may apply to people taking metformin or glucophage (medicines used to treat diabetes). If you are taking this medication, ring the number on your CT appointment letter.
Things you must tell us
You must tell us if you answer 'yes' to any of the following questions. Call the number on your CT appointment letter if:
- you have ever had an allergic reaction to intravenous CT or x-ray contrast
- you are, or think you could be, pregnant
- you suffer from asthma or diabetes
- you have a phaeochromocytoma (high blood pressure due to a tumour near the kidney)
- you have a condition called myasthenia gravis (a condition causing severe muscle weakness)
- you have any disorders of the blood or bone marrow
- you take a drug called metformin or glucophage
- you take a drug called interlukin 2
After your examination
After your examination, we ask you to stay in the CT waiting area for 20 minutes. We recommend that you don't drive a car or operate machinery for 40 minutes after leaving the CT department.
Intravenous x-ray contrast is very safe, but can cause a temporary mild sensation of warmth or a metallic taste in the mouth.
Symptoms you need to tell us about immediately
Occasionally, contrast can cause unwanted effects. If you suffer from any of the following, tell the doctor, radiographer or x-ray nurse immediately:
- wheeziness, difficulty in breathing or tightness or pain in the chest
- dizziness or feeling faint
- fever or high temperature
- an unexpected change in the amount of urine produced and / or its appearance
- stinging pain at or near the injection site immediately following the injection
- severe rash with peeling
If any of these symptoms develop after you have left the CT department, contact us on +44 (0) 1534 442844. After 5pm or weekends, call the hospital Emergency Department on +44 (0) 1534 442246.
If you need to have a thyroid function test within two weeks of having intravenous X-ray contrast, tell your doctor before the test is performed.
Other symptoms and when you should report them
Occasionally, people experience the symptoms listed below during or after their examination. These are usually mild and don't last long. If they become severe or last for more than a few days, contact your GP:
- abdominal discomfort
- nausea and or vomiting
- swelling or tenderness of your salivary glands on your throat
- pain during the injection
- low pulse and feeling faint
- skin rash, itchy spots or other allergic symptoms
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