Chylothorax and pseudochylothorax.

Chylothorax is the occurrence of chylus (lymph) in the pleura due to damage to the thoracic duct. There is a high content of triglycerides, and chylomicrons can be seen. It is usually right-sided, since most of the duct is within the right hemithorax. With damage at the level of the aorta, the chyle will appear on the left. Traumatic rupture occurs after accidents or surgery. Of nontraumatic causes, the most common is a malignant lymphoma. Computed tomography (CT) scan of the thorax and upper abdomen should be performed. Lymphography can show where the leakage or blockage is situated. With repeated drains, large amounts of fat, proteins, and lymphocytes are lost. Treatment is with low-fat diet or parenteral nutrition to decrease the amount of chyle, but chemical pleurodesis or ligation of the thoracic duct, usually via thoracoscopy, is often necessary. Pseudochylothorax (cholesterol pleurisy) occurs with long-standing fluid in a fibrotic pleura. The fluid has a high content of cholesterol but no triglycerides or chylomicrons. In both conditions, the pleural fluid is thick, opalescent, whitish or the colour of cafe-au-lait.