日本小児循環器学会雑誌 Pediatric Cardiology and Cardiac Surgery

Chylothorax, which occurs when chyle accumulates in the pleural space, is a common postoperative complication of congenital heart surgery. Recently, the number of neonatal cardiac surgeries or right heart bypass procedures has increased, thus leading to a corresponding increase in the incidence of chylothorax. Chyle is formed by chylomicrons that are transformed from long-chain triglycerides in the intestine. The diagnosis of chylothorax is confirmed by the presence of a triglyceride level of >110 mg/dL and >80％ lymphocytes per 1000 white blood cells/µL in a pleural aspirate. In congenital heart surgery, chylothorax typically results from three etiologies: 1) injury of a thoracic lymph duct, 2) elevation of systemic venous pressure due to thrombosis in the innominate vein or due to right heart bypass, and 3) congenial absence of a thoracic duct. Conservative management includes fat-free diets, middle-chain triglyceride milk, total parenteral nutrition, and treatment with somatostatin or octreotide. Invasive options include pleurodesis, thoracic duct ligation, or a pleuroperitoneal shunt. Although the optimal management of chylothorax remains controversial, evaluation of the central lymphatic system in pediatrics has drastically changed. For example, new management options, dynamic contrast-enhanced magnetic resonance lymphangiography, direct catheter interventions into the thoracic duct, and lymphatic venous anastomosis have been developed. Despite these, further improvements are needed in the treatment of chylothorax.