Congenital pyriform sinus fistula: a cause of acute left-sided suppurative thyroiditis and neck abscess in children.

Acute bacterial thyroiditis or neck abscesses in children can be caused by infection through pyriform sinus fistulae which usually originate from the tip of the left pyriform sinus. They are thought to be remnants of either the third or fourth pharyngeal pouches. CT, ultrasound and gastrointestinal contrast studies are all useful in clarifying the pathological process and showing the extent.