Riedel's thyroiditis: A case report and review of the ultrasound findings of this rare disease entity.

Introduction: Riedel's thyroiditis is a rare inflammatory disease of the thyroid with non-specific and varied presentations. A typical presentation and ultrasound findings are reported in this case.

Case report: A 68-year-old male is referred to Ear, Nose and Throat for a neck lump that varied in size over 2 years. An ultrasound scan identified a suspicious nodule on the left thyroid that was biopsied confirming the diagnosis of Riedel's thyroiditis.

Discussion: The aetiology, presentation and management of Riedel's thyroiditis are explored. The use of ultrasound and the utility of other imaging and biochemical tests are discussed.

Conclusion: Riedel's thyroiditis is a difficult condition to diagnose due to rarity, varied presentation, with non-specific clinical, biochemical and radiographic findings which often mimic thyroid cancers. Definitive diagnosis of Riedel's thyroiditis requires histological analysis, and while fine-needle aspirations are typically insufficient, diagnostic samples can be taken with ultrasound-guided core biopsies.