Pyriform sinus fistula: an unusual cause of recurrent retropharyngeal abscess and cellulitis.

Recurrent retropharyngeal cellulitis and recurrent suppurative thyroiditis are rare entities that share a common cause. A congenital fistula from the pyriform sinus apex to the thyroid gland has been identified in approximately 23 cases of suppurative thyroiditis and now has been implicated in a case of retropharyngeal abscess and repeated episodes of cellulitis. Virtually all reported cases have been on the left side, and the fistula is usually identified with a barium swallow study. When the esophagogram fails to demonstrate a fistula, a careful endoscopic search in the area of the left pyriform sinus should be actively pursued. An external surgical approach, which includes resection of the entire tract and involved area of the left thyroid, has been curative in all reported cases subjected to definitive surgical exploration.