Rectosigmoid ischemia and cerebral coma following gadolinium-induced anaphylaxis: A new manifestation of Kounis syndrome presented as devastating complication.

Gadolinium-based contrast mediums are the most commonly used agents in magnetic resonance imaging for both angiography, and brain tumor enhancement due to their association with the degradation of the blood-brain barrier. When oxidation is removed from gadolinium medium and gadolinium salts, a silvery-white metal anions remain that are able to induce allergic reactions and anaphylaxis. Whereas such reactions are not common, other reactions including nephrogenic systemic fibrosis and acute kidney injury due to primary excretion of gadolinium from the kidneys and various cardiac arrhythmias including QTc electrocardiographic prolongation are occasionally encountered 1,2. Despite that gadolinium-based contrast mediums are characterized as benign agents, in some occasions they can lead to life threatening conditions and Kounis syndrome 2-5. The concurrence of acute coronary syndromes such as coronary spasm, acute myocardial infarction, and stent thrombosis, with conditions associated with mast-cell and platelet activation involving other interrelated and interacting inflammatory cells, such as macrophages and Tlymphocytes in the setting of allergic or hypersensitivity and anaphylactic or anaphylactoid insults constitute the Kounis syndrome 6. This syndrome is caused by inflammatory mediators such as histamine, neutral proteases, arachidonic acid products, platelet-activating factor, and a variety of cytokines and chemokines released during the degranulation process of these inflammatory cells. Platelets bearing specific fragment crystallizable region receptors are also involved in the activation cascade 7. All these inflammatory cells participate in an inflammatory cycle and activate each other via multidirectional signals.