Understanding Contrast Agents

In diagnostic imaging it’s very important to use a contrast agent. Contrast agents are, by definition, “Also called a contrast medium, this is usually a barium or iodine dye that is injected into the area under investigation. The dye makes the interior body parts more visible on an x-ray film.” So the contrast agent is necessary although from case to case the reaction of a patient may differ.

In urology there is a need for contrast agents in various types of examinations. Urology depends on various types of diagnostic imaging examinations such as the MRI, the CT scan and many others to help diagnose conditions and establish a particular form of treatment. The following list is an example of procedures employing the use of imaging and contrast agents:

1. Intravenous Pyelography
2. Retrograde Pyelography
3. Retrograde Urethrogram
4. CT Scan
5. MRI
6. Angiography
7. Venography
8. Radionuclide Imaging
9. Cystography

TYPE	GENERIC NAME	IODINE, mg/mL	OSMOLALITY, mOsm/KG	VISCOSITY, CPS AT 37° C
Iso osmolar
Nonionic dimmer	Iotrolan	300	320	8.1
Nonionic dimmer	Iodixanol	320	290	11.4
Low osmolar
Ionic dimmer	Meglumine ioxaglate	320	580	7.5
Ionic dimmer	Sodium oxalate	320	580	7.5
Nonionic monomer	Iopamidol	300	616	4.7
Nonionic monomer	Iohexol	300	640	6.3
Nonionic monomer	Ioversol	300	645	5.5
Nonionic monomer	Iopromide	300	610	4.6
High osmolar
Ionic monomer	Sodium iothalamate	325	1843	2.75
Ionic monomer	Meglumine diatrizoate	306	1530	5.0

The contrast agent does have some risks to it but its purpose is to help physicians create a far better image and sometimes a road map in order to determine what course of action to take in favor of a patient. Urology imaging procedures can be daunting to think about but they serve a great purpose. Often times there are imaging tests that are performed without the use of any kind of contrast agent.

There are some risks to using contrast agents

The most common element in contrast agents is iodine. Iodine has radiopacity, defined as obstructing the passage of radiant energy. Other elements in contrast agents simply serve the purpose of reducing toxicity and increasing solubility in order to avoid adverse effects as much as possible. Contrast mediums do have side effects as does anything in healthcare. The contrast medium reactions vary from patient to patient and in terms of severity.

An example of minor reactions can include the following:

1. Nausea
2. Headache
3. Urticaria

More severe reactions require treatment but are likely to occur to one out of every 1,000 patients injected with contrast mediums. The contrast agent is not always easy to bypass all the way simply because often times a basic procedure may miss something and lead to a manner of treatment that may be inadequate and create another problem. Most studies presumed not to require the use of contrast agents, now require it. The MRI is an example of a scan that was thought not to need contrast agents but requiring it now. The following is a table of properties for commonly used radio contrast media: