Pyriform sinus fistulas are an unusual cause of neck cystic lesions in neonates. A definitive diagnosis requires detection of the fistula, which originates from the pyriform sinus and extends to the cystic lesion. Sonography has been reported to be useful for detecting fistulas. However, there have been no reports of neonatal cases in which sonography could detect fistulas not detected by other modalities, such as barium esophagography, computed tomography (CT), or magnetic resonance imaging (MRI). We describe five neonatal patients with pyriform sinus fistula-appearing cervical cystic lesions. All patients were examined by sonography; of these, three patients were also examined by barium esophagography, two by CT, and one by MRI. The fistula was detected by sonography but not CT in one patient and by barium esophagography but not MRI in one. Two patients whose fistulas were detected by sonography had an oval-shaped and relatively small cystic lesion. One patient whose fistula could be detected only by barium esophagography had a relatively large cystic lesion. In two patients, whose fistulas were not detected by sonography or barium esophagography, sonography revealed air bubbles within the cystic lesions, and a pyriform sinus fistula was suspected. Without requiring ionizing radiation, sonography was thus useful in diagnosing pyriform sinus fistula-appearing cervical cystic lesions in neonatal cases. On the other hand, in two patients whose fistulas were not detected by sonography, the shape of the cystic lesion was polygonal or multicystic. In two of three patients with infectious signs, a fistula could not be detected. The shape and size of the cystic lesion and the presence of infectious signs may be important factors for detecting fistulas.
