Effective Thoracic Duct Ligation at T9 for Postoperative Chylothorax: A Case Report

Postoperative chylothorax after lung resection and mediastinal lymph node dissection is a rare complication that may be difficult to manage when conservative treatment is ineffective, and the thoracic duct or leak point cannot be identified intraoperatively. Chylothorax is thought to result from thoracic duct injury associated with mediastinal lymph node dissection. Although surgical thoracic duct ligation is recommended in refractory cases, identification of the leakage site or thoracic duct itself is often challenging, particularly in patients with intrathoracic adhesions or in facilities where lymphangiography cannot be performed. An 82-year-old man underwent thoracoscopic right upper lobectomy with mediastinal lymph node dissection for lung adenocarcinoma with mediastinal invasion after induction chemotherapy. Postoperatively, a pulmonary fistula and chylous effusion developed. Although the chylous effusion initially improved with conservative treatment, including a low-fat diet, massive right pleural effusion recurred after discharge. Pleural fluid examination revealed elevated triglyceride levels, leading to a diagnosis of chylothorax. Conservative treatment with dietary restriction and octreotide was ineffective, and thoracoscopic surgery was performed. During the reoperation, severe intrathoracic adhesions and thickening of the mediastinal pleura were observed due to prior surgery and pleurodesis. The areas of previous mediastinal lymph node dissection were carefully examined; however, no clear lymphatic fistula or thoracic duct was observed. Intraoperative intravenous indocyanine green did not delineate the thoracic duct. Because identification of the thoracic duct at the supradiaphragmatic level was considered difficult, the mediastinal pleura was incised at the T8-T9 level, where the thoracic duct anatomically runs between the azygos vein, descending aorta, and esophagus. The adipose tissue containing the presumed thoracic duct was ligated <i>en bloc</i> using silk sutures and resected. Chylous drainage decreased immediately after the procedure, and the chylothorax resolved without recurrence. At the T9 level, posterior mediastinal adipose tissue is relatively limited compared to that at the supradiaphragmatic level, making <i>en bloc</i> ligation feasible even when the thoracic duct cannot be directly identified. Ligation of the thoracic duct together with the surrounding adipose tissue at the T9 level may represent an effective alternative surgical option for postoperative chylothorax in cases where lymphangiography is unavailable or where intrathoracic adhesions make conventional thoracic duct ligation difficult.