Introduction
In 1973, the pyriform sinus fistula (PSF) was defined as a fistula that
originated from the remnant of the 4th pharyngeal
pouch.1 Then, in 1979, Takai et al. reported that
recurrent acute suppurative thyroiditis was caused by
PSF.2 Moreover, 3%–10% of congenital anomalies that
originated from the pharyngeal pouch have been known as remnants from
the 3rd and 4th pouch, which are considered as origins of PSF. It is
different from brachial cyst, so called lateral cervical fistula. The
inferior parathyroid glands and thymus that originated from the 3rd
pouch moves caudally, whereas the superior parathyroid gland and C cells
producing calcitonin that originated from the 4th pouch migrate caudally
behind thyroid gland.3 These two tracts are considered
as routes of PSF and sometimes presented as two simultaneous fistulas
with two different origins as previously reported.4Most PSFs (93.5%) are located on the left side because the left side
shows more complex vascular development and that the C cell precursor,
ultimobranchial body, and part of the 4th pouch develop from the left
side.5-7
The diagnosis of PSF is confirmed by fluoroscopy and/or computed
tomography with enhancement by barium swallow with Valsalva
technique.5 The decision of radical treatment of PSF
depends on the frequency of recurrent acute onset and severity of acute
phase with attentive consultation with patients and family members. In
1998, Jordan et al. proposed endoscopic cauterization of
PSF8 although this palliative treatment frequently
causes recurrences (25%) as reported in 15 previous
studies.9 In contrast, 18 cases of surgically complete
fistulectomy in India presented no recurrence.10
There were case reports on severe acute suppurative thyroiditis and deep
neck abscess caused by PSF, but no report has mentioned about the routes
and origins of PSF. We analyzed 19 cases of completely resected PSF and
found two different pathways of fistulas at surgery. In this study, we
distinguished two origins of PSF and compared their routes, histology,
and clinical manifestations to understand the pathology and improve
treatment of PSF.