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Also see Pleural Effusion.
Chylothorax is a pleural effusion caused by the leakage of lymphatic fluid into the pleural space from a ruptured thoracic duct or obstruction of the lymphatic vessels.
Causes: Malignancy (most commonly lymphoma or metastases of other cancers); injury, including surgery (particularly of the esophagus), chest trauma, sometimes catheterization of the superior vena cava; lymphangioleiomyomatosis; obstruction of a vena cava; amyloidosis; tuberculosis.
Diagnosis is made on the basis of pleural fluid analysis. The fluid is milky-white and odorless and contains chylomicrons. The level of triglycerides is usually >1.24 mmol/L (110 mg/dL), no cholesterol crystals are present, and the level of cholesterol is <2.59 mmol/L (100 mg/dL).
Chylothorax has to be differentiated from pseudochylothorax, which occurs very rarely and is a result of the accumulation of cholesterol in a chronic pleural effusion. Usually it develops in the course of a chronic pleural effusion, such as in tuberculosis or rheumatoid arthritis. The pleural fluid in pseudochylothorax has the same appearance as in chylothorax, but the level of cholesterol is >5.18 mmol/L (200 mg/dL), cholesterol crystals are present, and the level of triglycerides is usually <0.56 mmol/L (50 mg/dL).
Treatment includes pleural drainage and management of the underlying disturbances. Evaluation by a dietitian and instructions on a high-protein low-fat (<10 g/d) diet are recommended. Total parenteral nutrition to reduce lymph production and close the fistula between the lymph vessel and the pleural space can also be considered if oral therapy is insufficient. Somatostatin and octreotide can be used as adjunctive therapies. In two-thirds of patients chylothorax resolves after 12 to 14 days. A constant lymph outflow >500 mL/d is an indication for surgical treatment.