BackgroundChylothorax, a rare but serious complication following esophagectomy, can lead to dehydration, malnutrition, and even mortality. Surgical intervention is considered when conservative treatment is ineffective; however, in some refractory cases, the cause of chylothorax remains unclear. We report a case of refractory chylothorax caused by abdominal chyle leakage into the pleural space via an unenclosed esophageal hiatus.Case presentationA 66-year-old man was diagnosed with advanced esophageal squamous cell carcinoma. The patient underwent robot-assisted thoracoscopic subtotal esophagectomy in the prone position with retrosternal gastric tube reconstruction following neoadjuvant chemotherapy. The thoracic duct was ligated and resected because of tumor invasion. Chylothorax and chylous ascites were observed 2 weeks after surgery but did not improve despite conservative management with medications and drainage. Lymphoscintigraphy through the inguinal lymph node showed tracer accumulation in the fluid in both the abdominal and pleural spaces. Lipiodol lymphangiography revealed abdominal lymphoid leakage, but no leakage was detected from the thoracic duct or mediastinum. We considered that the chylothorax was caused by chylous ascites flowing into the pleural space via an unenclosed esophageal hiatus, and we performed surgical intervention. Laparotomy revealed abdominal chyle leakage and a fistula at the esophageal hiatus with the inflow of ascites into the thoracic cavity. Lipiodol lymphangiography was additionally performed for treating abdominal lymphorrhea after surgery, and resulted in the improvement of the chylothorax and ascites. The patient was discharged with no recurrence of chylothorax or chylous ascites.ConclusionsRefractory chylothorax can occur due to chylous ascites flowing into the pleural space via an unenclosed esophageal hiatus. When the site of chylothorax leakage is unclear, the possibility of inflowing chylous ascites via the unenclosed esophageal hiatus should be explored. Esophageal hiatus closure and lipiodol lymphangiography could be effective in treating refractory chylothorax of unknown cause after esophagectomy.