What is a radiographic contrast agent?
A radiographic contrast agent is a substance that is administered to a patient during an imaging examination to improve its diagnostic performance. Contrast agents are most often administered via the intravenous (IV) and oral routes for computed tomography (CT) and magnetic resonance imaging (MRI) examinations. However, other routes of contrast administration may be utilized, depending on the particular imaging study to be performed. For example, arteriography requires the intraarterial (IA) administration of contrast material, while arthrography requires the intraarticular injection of contrast material directly into a joint. Intrathecal contrast administration is required for myelography.
A catheter is used to inject the contrast material in some procedures. In hysterosalpingography, a catheter or cannula is placed into the external cervical os to opacify the uterine cavity. In retrograde urethrography, a Foley catheter is placed at the urethral meatus in a male to inject contrast material to evaluate the urethra. In cystography, injection of contrast material is performed through a catheter placed in the urinary bladder. In retrograde pyelography, contrast material is administered through catheters placed into the renal collecting systems with cystoscopic guidance to evaluate the pyelocalyceal systems and ureters in patients who cannot receive intravenous contrast material.
The administration of radiographic contrast agents by the various routes mentioned above is widely used in clinical practice, and is usually not associated with any adverse effects. However, prior to administering contrast material, attention must be given to the clinical indication for the procedure, and to the clinical status of the patient in order to minimize adverse side effects and to maximize diagnostic yield. It is essential that in a facility where contrast material is routinely administered for imaging studies, trained personnel along with appropriate equipment and medications be available on site to manage a contrast reaction, should one occur.