Patient evaluation for contrast administration for computed tomography: Concern for acute contrast reaction

CT: computed tomography.
* Refer to UpToDate topics or the American College of Radiology (ACR) Appropriateness Criteria for CT contrast recommendations based on a specific exam indication.
¶ Acute reaction to contrast can occur after oral, intracavitary, or intravascular administration. Verify that the reaction was to iodinated contrast (used for CT, radiography, fluoroscopy, or angiography) rather than to noniodinated contrast used for other imaging modalities (eg, gadolinium, used for magnetic resonance imaging), as there is no cross-reactivity between the two classes. If the reaction was delayed (>20 minutes) it is not considered an acute reaction.
Δ Refer to the inset box titled "Clinical manifestations of acute contrast reaction" to classify reaction.
◊ Refer to UpToDate topic for commonly used premedication prophylaxis regimens. For outpatients, one option is three doses of 50 mg oral prednisone administered 13, 7, and 1 hour prior to contrast administration; and 50 mg oral diphenhydramine administered one hour prior to contrast administration.
§ Imaging alternatives are CT without contrast, ultrasound, magnetic resonance imaging, or nuclear scintigraphy. Discuss with a radiologist whether any of these are likely to provide a diagnosis.
¥ Examples of such scenarios are extremely rare and may include CT angiography for diagnosis of acute aortic injury or dissection.