Occult congenital pyriform sinus fistula causing recurrent left lower neck abscess

Background. Congenital pyriform sinus fistula (CPSF) is a rare branchial pouch anomaly; it has the characteristic of left-sided predominance and is not always detected until complications such as neck abscess or acute suppurative thyroiditis resulted. Method. Seven sequential cases of CPSF, including five adults and two children, causing recurrent left lower neck abscess were reported. All of these patients had past histories of misdiagnosis: the intervals from the onset of symptoms to correct diagnosis ranged from 3 years to 34 years with an average of 20 years. Results. After barium swallow study and direct laryngoscopic examination in the quiescent stage of infection, the CPSFs of these seven patients were successfully excised with or without catheter guide. Conclusion. The key to diagnosis of CPSF is a high index of suspicion by the clinician. CPSF should be considered in the differential diagnosis of a neck abscess, especially if it is recurrent and left-sided.