Steroid Premedication Fails to Prevent Recurrent Iodinated Contrast‑Induced Salivary Gland Swelling in a 75‑Year‑Old Woman

A 75‑year‑old woman in Thailand developed painful swelling under both sides of her jaw 16 hours after receiving iodinated contrast for a repeat CT scan, despite having been premedicated with oral prednisolone because of a similar reaction a decade earlier. The episode was diagnosed as recurrent contrast‑induced sialadenitis, a condition also known as “iodide mumps.”

The case, reported on September 12 in American Journal of Case Reports, comes from two radiologists at Ramathibodi Hospital, Mahidol University, Bangkok. The authors describe the event as a rare, delayed, non‑allergic reaction that can reappear with subsequent contrast exposure.

A Second Reaction a Decade Later

The patient, who has stage 3a chronic kidney disease, was referred for a contrast‑enhanced chest CT to evaluate long‑standing bronchiectasis. She recalled that about ten years prior she had experienced neck and sub‑mandibular swelling shortly after an intravenous contrast injection. Based on that history, she was prescribed oral prednisolone as premedication for the new scan.

After receiving the iodinated agent iopromide, she returned to the hospital with painful, bilateral swelling beneath her jaw. Physical examination revealed firm, mildly tender swelling of both sub‑mandibular glands without overlying skin erythema or drainage from the ductal openings. Importantly, there was no laryngeal edema or airway spasm, ruling out a classic allergic reaction.

Ultrasound Pointed to the Contrast Dye

Ultrasound showed diffuse enlargement of both sub‑mandibular glands with heterogeneous echotexture, increased vascular flow, and mild dilation of the intraglandular ducts. No salivary stones or abscess—common alternative causes of gland swelling—were identified.

Given the timing and imaging findings, the clinical team diagnosed a recurrence of contrast‑induced sialadenitis in both glands.

Conservative management with warm compresses and oral analgesics resulted in complete symptom resolution within four days.

The authors emphasize that recognizing the characteristic features of this reaction can prevent misdiagnosis and avoid unnecessary contrast exposure, premedication, and further testing.

A Reaction First Described in 1956

Iodide mumps was first documented in 1956 in the New England Journal of Medicine. A later meta‑analysis aggregated 77 cases across 65 reports, reporting a median onset of 16 hours and resolution in three days. Patients often had impaired renal function, and low‑osmolarity non‑ionic contrast agents were most frequently implicated.

The true incidence remains uncertain. Some large series reported no cases, while other estimates place the frequency at roughly 1–2 % of contrast administrations. A 2022 study of 780 neuroendovascular procedures found an incidence of 4.2 %, with higher rates associated with female sex, larger contrast volumes, and guiding‑catheter positioning.

The pathophysiology is not fully understood. Early ideas of an antibody‑mediated allergy have been discarded; current consensus describes the reaction as pseudo‑allergic. One hypothesis suggests that contrast material accumulates in the salivary glands, triggering local inflammation.

Does Steroid Premedication Help?

The Thai report adds to a modest body of literature indicating that steroids may not reliably prevent iodide mumps. Japanese clinicians described a 60‑year‑old man whose neck swelling recurred twice despite prednisolone therapy and a switch to a different contrast agent. Israeli allergists reported similar failures in 2008 and recommended non‑iodinated imaging for patients with a prior reaction.

Evidence is mixed; at least one case series suggested that steroids appeared to halt a third episode in a man with two previous reactions. The Japanese authors concluded that the preventive value of steroids remains unclear because of the scarcity of reported cases.

Renal dysfunction may influence contrast clearance and glandular accumulation, yet meta‑analysis data showed no difference in symptom resolution time between patients with normal and impaired kidney function. A 2023 report described a 40‑year‑old woman with normal renal function who developed painless sub‑mandibular swelling after a brain CT using a low‑volume (40 mL) contrast regimen.

Overall, iodide mumps is self‑limited, but a detailed history of prior reactions is crucial for guiding future imaging decisions.

Patients who experience facial, neck, or jaw swelling after a contrast‑enhanced CT should inform their clinical and radiology teams before any subsequent scans. Any swelling accompanied by breathing difficulty, throat tightness, or wheezing warrants immediate emergency care.

Key Questions Answered

What is iodide mumps?

It is swelling and inflammation of the salivary glands that can develop minutes to days after exposure to iodine‑based contrast used in imaging studies.

Is it an allergic reaction?

No. The authors classify it as a delayed, non‑allergic (pseudo‑allergic) reaction, likely due to contrast accumulation in the salivary glands rather than an immunoglobulin‑E–mediated process.

Why was this case notable?

The patient had a comparable reaction a decade earlier, and the swelling recurred despite steroid premedication, highlighting the limited protective effect of steroids in some individuals.

Do steroids prevent it?

Evidence is limited and contradictory. Several reports describe recurrence despite steroids, while a few suggest possible prevention. Consequently, the role of steroid premedication remains uncertain.

What should patients with a past reaction do?

They should disclose any prior contrast‑related swelling to their clinicians and imaging teams so alternative strategies (e.g., non‑iodinated agents) can be considered. Any signs of respiratory compromise after contrast require immediate medical attention.

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