O-24 UNEXPECTED COMPLICATIONS AFTER RADIOFREQUENCY ABLATION: A CASE OF ABSCESS AND SEVERE HYPERTHYROIDISM

Abstract Introduction Radiofrequency ablation (RFA) is a minimally invasive alternative to surgery for selected patients with benign thyroid nodules, particularly those with cosmetic concerns or compressive symptoms. However, inappropriate patient selection may lead to avoidable complications. Reports on the use of RFA for hyperfunctioning thyroid nodules remain limited. We present a patient who developed overt hyperthyroidism and abscess formation after RFA of a large toxic thyroid nodule. Clinical Case A 51-year-old female with a history of multinodular goiter, Behçet’s disease, and prior surgery for head-and-neck paraganglioma (glomus caroticum tumor) initially presented to another center with anterior neck swelling. On admission, her vital signs were stable, and physical examination revealed a palpable, externally visible left thyroid lobe nodule (∼4 cm) associated with compressive and cosmetic symptoms. Thyroid ultrasonography demonstrated multinodular goiter: the largest lesion in the left lower lobe measured 42 × 28 mm, mixed solid–cystic, EU-TIRADS 3; in the right upper lobe measured 18 mm, heterogeneous mixed, also EU-TIRADS 3. As the patient had a nearly 10-year history of subclinical thyrotoxicosis, thyroid scintigraphy was performed, showing heterogeneous uptake with focal hyperfunction in the right upper and left middle–lower poles (Figure 1). Given the patient’s preference to initially consider non-surgical treatment options, RFA was performed on the 25-cm³ left lower lobe nodule (18G microwave probe, 30 W, 13 min 10 sec) in another center. Within one week, the patient developed neck pain, swelling, fever, and erythema; imaging confirmed an abscess at the ablation site with cutaneous fistula formation. She received intravenous antibiotics. During follow-up, overt hyperthyroidism developed with persistently elevated free thyroxine (fT4) levels. Methimazole was initiated and gradually increased to 60 mg/day due to resistant thyrotoxicosis. At this stage, the patient was referred to our endocrinology clinic while on high-dose methimazole therapy (Table 1). Definitive surgical management was planned after stabilization of thyroid function. Conclusion This case illustrates that RFA in toxic thyroid nodules is not a standard therapy of choice. When considered, particularly for large nodules, multiple treatment sessions may be required. Complications such as abscess and fistula formation can occur, potentially aggravated by comorbid conditions like Behçet’s disease. Established modalities such as radioactive iodine (RAI) or surgery remain the preferred treatments, and RFA should be reserved for carefully selected cases.Figure 1:Thyroid scintigraphy demonstrating heterogeneous uptake of radioisotope in both lobes, with markedly increased focal activity in the right upper pole and left middle–lower pole consistent with hyperfunctioning nodules (indicated by red arrow Table 1:Thyroid function tests (TFTs) before and after radiofrequency ablation (RFA), and during methimazole titration.