Piriform sinus fistula. A route of infection in acute suppurative thyroiditis.

Fifteen patients had acute suppurative thyroiditis resulting from infection through the left piriform sinus fistula. Characteristic clinical features included (1) onset in infancy or childhood, (2) left lobe involvement, and (3) frequent recurrence unless the fistula was extirpated completely. Fistulectomy in eight patients demonstrated three distinct courses of the fistula: lateral to, medial to, and penetrating the left thyroid lobe. Anatomical and histological findings suggest that the fistula is a remnant of the third pharyngeal pouch. We believe that the fistula is a common route of infection in acute suppurative thyroiditis, allowing bacterial infection to begin either in the perithyroidal space, spreading into the thyroid gland secondarily, or in the thyroid gland, primarily in cases where it penetrates the gland. Complete removal of the fistula is essential to a permanent cure.