OBJECTIVE:Chylous fistulas can occur after neck surgery. Both nonoperative measures and direct fistula ligation may lead to fistula resolution. However, a refractory fistula requires upstream thoracic duct ligation. This can be accomplished minimally invasively. Success depends on lymphatic flow interruption where the duct enters the thorax. We report on the utility of frozen section confirmation in achieving this goal. METHODS:Persistent chylous fistulas occurred in 2 patients after left cervical operations. In the first patient, attempted direct fistula ligation and sclerosant application failed. Fasting, parenteral nutrition, and somatostatin-analog provided no benefit. For the second patient, nonoperative treatment was also ineffective. Prior radiation therapy and multiple cervical operations militated against attempted direct fistula ligation. Both patients underwent thoracoscopic thoracic duct interruption. RESULTS:In both cases, a duct candidate was identified between the aorta and azygos vein. Frozen section analysis of tissue resected between endoclips verified it as thoracic duct. Fistula resolution ensued promptly in both instances. CONCLUSIONS:This report lends further credence to the efficacy of minimally invasive thoracic duct ligation in treating postoperative cervical chylous fistulas. Frozen section confirmation of thoracic duct tissue is useful. It allows one facile with thoracoscopy, but less familiar with thoracic duct ligation, to confidently terminate the operation.