Acute suppurative thyroiditis (AST) and thyroid abscess are rare, accounting for less than 1% of all thyroid diseases. The thyroid gland is considered resistant to infection due to its rich blood supply, encapsulation, and iodine-rich environment. Common causative organisms include Streptococcus, Staphylococcus aureus, and anaerobes. Escherichia coli (E. coli) is seldom implicated, and thyroid abscesses due to E. coli bacteremia are extremely uncommon. We present an elderly patient with multinodular goiter complicated by thyroid abscess secondary to E. coli, highlighting diagnostic and therapeutic considerations.

An 86-year-old woman with type 2 diabetes mellitus and history of bladder cancer presented with fever and dysuria. Blood and urine cultures grew E. coli, and complicated urinary tract infection with bacteremia was diagnosed. During hospitalization, progressive left anterior neck swelling and tenderness developed. Neck computed tomography revealed a left thyroid goiter (36 × 43 mm) with tracheal deviation but no lymphadenopathy. Thyroid ultrasound demonstrated an irregular hypoechoic mass with calcification. Fine-needle aspiration (FNA) performed on two separate occasions within one week yielded frank pus, which cultured E. coli.

Esophagography excluded pyriform sinus fistula or esophageal leakage. A diagnosis of acute suppurative thyroiditis with thyroid abscess, superimposed on multinodular goiter, was established. The patient received prolonged intravenous antibiotics (guided by culture sensitivity) with gradual clinical improvement. No surgical drainage was required.

Thyroid abscess due to E. coli is exceedingly rare, especially in elderly patients with pre-existing thyroid abnormalities. This case illustrates that hematogenous seeding from bacteremia may overcome the natural resistance of the thyroid gland, particularly in immunocompromised or structurally abnormal glands. Clinicians should maintain a high index of suspicion when bacteremia coexists with new neck swelling, even when the pathogen is atypical. Early recognition and appropriate antimicrobial therapy are critical to avoid airway compromise and invasive intervention. This case contributes to the limited literature on E. coli thyroid abscess and underscores the importance of considering unusual pathogens in high-risk populations.