Why Would I Need Contrast Media In My Radiology Examination?

A number of investigations in Radiology will require administration of this contrast into your body via a vein or artery. A common example is the intravenous urogram. There are two type of iodine containing contrast media, and these are either ionic or non-ionic (with regards to its chemical structure).

If you have none of the following conditions, you would probably only need to fast (no food or drink) for 4-6 hours prior to the examination.

• If you have the following conditions, you will need to take special precautions and be aware of the slightly increased risks:

• Definite History of Allergy

• Asthma

• Previous reaction to contrast media

• Previous reaction to drugs

• Heart conditions

• Multiple Myeloma or myelodysplastic syndromes or severe diabetes (please do not dehydrate yourself by restricting your water intake)

• The very old (> 65 years) and the very young < 6 months>        

If you have allergies or previous reactions, you may be asked to take Prednisolone 40 mg 12 hours and 40 mg, 2 hours prior to the examination. The need for the examination will have to be weighed against the risk. Your doctor requesting the examination normally prescribes this. If you are unsure if you have risk factors, please inform your doctor of any suspected allergies or other health conditions.

For those with Multiple Myeloma or myelodysplastic syndromes, you should be well hydrated and should be encouraged to drink fluids for the examination such as the Intravenous Urogram (IVU).

The type of intravenous contrast used in the above patients would always be a non-ionic contrast medium.

If you are diabetic and on Glucophage (Metformin): Please stop your medication 48 hours prior to doing an examination requiring intravenous or intra-arterial contrast media injection.

Despite what may appear as alarming in the descriptions below, the incidence of the moderate to severe reactions are extremely low. Your doctor would have considered the benefits versus risk ratio when they recommended certain investigations for you. It may be more risky to cross a busy road then to undergo an examination that may help to diagnose and your doctor to treat your condition better.

Contrast medium is like other drug you may be more familiar with. In fact, the new generation of iodine containing contrast media are very safe. Even so, like all drugs, (including the commonly taken Panadol/Paracetamol), there is a potential risk of reaction to the contrast media. These are classified into mild, moderate and severe. With the non-ionic contrast media, the incidence of reactions is markedly reduced. Most of the reactions are mild, transient and require no treatment, and the majority will occur within the first 20 minutes of the injection. There are a small proportion of delayed reactions, which may occur up to a day or two after the injection.

Examples include:

Mild:

• Nausea, vomitting and/or both.

• Generalised transient warmth felt throughout the body. (akin to flushing)

• Rashes which may be transient or lasting a few days. An antihistamine will be given.

• Sneezing, “running” nose.

Moderate:

• Difficulty breathing, (it may be like asthma): immediate treatment given. Rarely, this is so severe to be life threatening.

• Hypotension: Sudden drop in the blood pressure: Immediate treatment given. Usually this is transient and not severe.

Severe and life threatening ( VERY RARE with modern iodine containing contrast medium):

Anaphylactic shock. (an unpredictable reaction)

This would depend on the procedure that was done.

However, in general, you are encouraged to drink plenty of fluids and maintain hydration. The majority of the iodine containing contrast medium would be excreted into your urine within 4 hours after the examination.

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Last Updated:
Thursday, 21 August, 2003