Radiocontrast media hypersensitivity
Radiocontrast media hypersensitivity is usually an anaphylactoid (non-IgE) reaction from direct mast cell mediator release, clinically resembling anaphylaxis, though delayed T-cell-mediated reactions also occur. Risk falls with low-osmolar nonionic agents, and high-risk patients are managed with a corticosteroid and antihistamine premedication protocol, with acute reactions treated like anaphylaxis.
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What this article covers
- Overview
Definition: radiocontrast media hypersensitivity is an adverse reaction to iodinated contrast that clinically mimics anaphylaxis but is usually anaphylactoid, arising from direct (non-IgE) mast cell mediator release.
- Epidemiology
Immediate reactions are the classic concern, more frequent with intravenous than intra-arterial administration.
- Risk factors
Prior reaction to iodinated contrast: the single strongest predictor.
- Pathophysiology
Anaphylactoid mechanism: contrast triggers direct mast cell and basophil mediator release without drug-specific IgE, so a first exposure can react.
- Clinical features
Immediate reactions: urticaria and flushing (mild), progressing to angioedema, bronchospasm, and hypotension (severe), within minutes of injection.
- Differential diagnosis
True anaphylaxis from another agent: a concurrently administered drug or latex, distinguished by a temporal link to that agent rather than to the contrast injection (Anaphylaxis).
- Diagnosis
Diagnose clinically by the temporal relationship and phenotype, classifying immediate versus delayed: the diagnostic basis is a reaction (urticaria, angioedema, bronchospasm, or hypotension)…
- Management
First-line, treat an acute reaction as anaphylaxis: For a severe immediate reaction, epinephrine 0.3 to 0.5 mg IM into the anterolateral thigh, repeated every 5 to 15 minutes as needed, with oxygen, IV fluids, and airway support.
- Complications
Anaphylactoid shock: the principal acute danger.
- Prognosis
Good with modern agents and premedication: most reactions are mild and preventable, and severe reactions are uncommon.
- Prevention
Use low-osmolar nonionic contrast to minimize reaction risk.
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Related articles
- Anaphylaxis
Anaphylaxis is an acute, potentially fatal systemic hypersensitivity reaction from massive mast cell and basophil mediator release, presenting within minutes as skin, respiratory, cardiovascular, and gastrointestinal involvement after allergen exposure. It is a clinical, treat-first diagnosis, and intramuscular epinephrine is the immediate life-saving therapy.
- Urticaria
Urticaria is transient, pruritic, edematous wheals from mast cell histamine release, classified by duration into acute (under 6 weeks) and chronic (6 weeks or longer, usually spontaneous/idiopathic). Diagnosis is clinical with minimal testing, and treatment is stepwise second-generation H1 antihistamines up-titrated as needed, adding omalizumab for refractory chronic disease.