Introduction

Anaphylactic shock is a severe, life-threatening allergic reaction that can result from exposure to contrast agents used in imaging procedures [1]. Reactions to iodine-based contrast media are a serious but relatively uncommon complication in radiology [2]. Such instances require urgent attention because of their tendency to progress to a life-threatening condition. Iodinated contrast media (ICM) are among the most widely used pharmacological agents in diagnostic radiology, administered an estimated 75 million times annually worldwide to enhance the visualization of soft tissues, vascular structures, and tumors on computed tomography (CT) imaging. Despite their widespread and generally safe use, anaphylactic deaths still occur at a rate of approximately one to three per 100,000 to 1,000,000 administrations [1]. In breast cancer patients, CT imaging plays a vital role because it not only assesses the primary tumor but also evaluates the extent of metastatic disease, helps in monitoring the treatment response, and guides the treatment options [3]. Nonionic and low-osmolar contrast agents such as Omnipaque and Visipaque have a decreased risk of inducing severe reactions compared with high-osmolar agents that were used commonly in the past. Nevertheless, hypersensitivity reactions still remain an important clinical concern, ranging from mild urticaria to life-threatening anaphylactic shock. Therefore, proper management strategies should be understood to increase patient safety in radiology and oncology departments [2].

Anaphylaxis is an acute, hypersensitivity reaction that affects multiple body systems and is triggered by exposure to allergens, including medications, foods, and contrast agents. The pathophysiology of iodine-based contrast-induced anaphylaxis is very complex because it involves both immunologic (IgE-mediated) and nonimmunologic pathways (direct activation of mast cells and basophils) [4]. Once activated, these cells release inflammatory mediators like histamine, tryptase, and cytokines, which cause symptoms such as hypotension, bronchospasm, urticaria, and, in severe cases, shock [1]. Severe reactions occur in approximately 0.01%-0.04% of cases, and minor reactions in 3%-5% [1,4-6]. Although these rates are low, minor reactions can be unpredictable and may progress to severe outcomes. This is why it is advisable to exercise high caution with established emergency treatment algorithms in these treatment areas.

A particularly vulnerable group is cancer patients, who undergo frequent contrast-enhanced imaging for staging, treatment monitoring, and surveillance. Immune compromise secondary to malignancy itself, chemotherapy, and immunomodulatory therapies may alter susceptibility to hypersensitivity reactions [4]. Furthermore, repeated ICM exposure in such a population increases sensitization risk [2,4].

Recent studies highlight the need for rapid identification and management of anaphylactic reactions due to the potentially fatal outcomes of ICM-induced anaphylaxis. A consensus guideline by the American College of Radiology (ACR) (2023) recommends that intramuscular epinephrine should be used immediately as the first-line treatment. Contrast administration should be discontinued immediately, while simultaneous supportive measures, including oxygen supplementation and intravenous fluid resuscitation, should be initiated. Additional therapies, such as antihistamines and corticosteroids, may be administered as adjunctive treatment but should never delay epinephrine administration [7]. Radiology departments should be equipped with structured emergency response protocols for ICM-induced anaphylaxis, and staff should be appropriately trained to handle these situations. This, in turn, can improve outcomes in severe contrast-related reactions [8,9].

Recent research has increasingly focused on premedication strategies using corticosteroids and antihistamines in patients with prior hypersensitivity reactions to ICM. Although these regimens reduce the risk of recurrent hypersensitivity reactions, they do not provide complete protection, and severe breakthrough reactions, including anaphylaxis, may still occur [10].

Although severe reactions to ICM are rare, they continue to occur in routine clinical practice. We present three cases of anaphylactic shock following ICM administration during CT imaging, including two patients with breast cancer and one patient with multiple comorbidities. None had a known prior history of contrast-related reactions or food allergies; however, Case 2 had a documented penicillin allergy. Despite established management guidelines, detailed case series describing severe iodinated contrast-induced anaphylactic shock, particularly comparing different clinical presentations and management pathways, remain limited. These cases collectively illustrate the unpredictable nature of contrast hypersensitivity, the importance of swift emergency management, and the need for robust institutional treatment protocols, which are pivotal and fundamental to improving patient outcomes.