Contrast Medium Information



As part of a number of examinations, you may need to have an injection of Radiographic Contrast Medium. This is a colourless dye that shows up on x-ray pictures and scans, and is used to highlight structures in the body that can't be seen without it. This contrast agent causes no complication in the vast majority of people who have it.

There are risks involved with any medical procedure; and in a small number of people, certain side effects can occur following an injection of contrast agent.

Many people describe a feeling of warmth around their body and an unusual taste in the mouth. This is normal and lasts for a minute or two. Brief nausea may occur. Some people develop minor allergic symptoms such as hives, itchiness or a stuffy nose or eyes.

Your doctor (who requested this test) is aware of the risks, and has recommended the test knowing the benefits of the examination far outweigh the tiny risk involved.

Patients with allergies

If you have:

  • Had a previous allergic reaction to a contrast medium
  • Have asthma
  • Have a strong history of allergies
  • Please discuss this with the staff when you make the appointment and when you come for your radiology test.

The Radiologist may suggest you have another radiology examination that doesn't require contrast media, or suggest you take something (eg antihistamine) prior to your appointment.

Patients using Metformin

An association has been found between the intravenous administration of contrast media and lactic acidosis, in patients with diabetes mellitus receiving Metformin. The association is rare, and happens only in patients with impaired renal function. If you have an examination needing contrast medium, you may need to stop taking the Metformin before your study and not start it again for two days. This will depend on a blood test of your kidney function. Your Doctor and the Radiologist will discuss the best method of imaging to meet your needs. Inform the receptionist you are taking Metformin, when you phone to make your appointment.

Examinations that use contrast medium are:

  • Some CT examinations
  • IVU
  • Hysterosalpingogram
  • Micturating cystogram {using a fine tube, contrast media is used to fill the bladder - eg used for children with recurrent urinary tract infection}
  • Sialography - to demonstrate the salivary glands - eg looking for calculus
  • Dacrocystography - to demonstrate the tear ducts in the eyes.
  • Arthrograms - now preferentially use other imaging such as musculo skeletal & MRI - contrast media is injected into the joint {eg shoulder, knee}.
  • Ductograms (of the breast)
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