[Clinical evaluation of patients with pyriform sinus fistula]. 
Thirteen patients with pyriform sinus fistula treated surgically at our department were clinically evaluated.  Twelve (92%) fistulae occurred in the left pyriform sinus, and one (8%) in the right.  There were a mean of 4 infectious episodes before the final diagnosis.  The median age at the first infection was 5 years, and the median age at surgery was 13 years, although there were 2 elderly patients (over 60 years old) in this series.  Association with pharyngeal foreign body was suspected in the case with onset at 81 years of age.  There was a history of previous surgery for cervical disease in 54% of the patients.  The final diagnosis was based on delineation of the fistula by hypopharyngography, although coronal section of CT and MRI were also useful for understanding the morphopathology.  The surgical procedure consisted of identification and staining of the fistula under direct hypopharyngoscopy, followed by identification and extirpation of the fistula until the distal end via a cervical approach.  There was no recurrence of infections, although resection of the thyroid gland and identification of the recurrent laryngeal nerve were not always performed.  The most important surgical principle is considered to be complete disconnection of the lesion from the hypopharynx, and complete identification and extirpation of the fistula by the procedure used at our department is considered to be a useful surgical strategy.