Q: One definition of chylothorax is pleural fluid's triglyceride level greater than 110 mg/dL.  What is the other definition of chylothorax, if triglycerides concentration does not reach at 110 mg/dL but clinically chylothorax seems highly suspected?


Answer:   Presence of chylomicrons

In about 20 percent of chylothorax, triglyceride in pleural fluid may not reach the cutoff number of 110 mg/dL. In such scenarios presence of chylomicrons in the pleural fluid is enough to label it as chylothorax. Major differential diagnosis of chylothorax is with cholesterol effusions, which may be diagnostic with the presence of cholesterol crystals. Chylomicrons are not present in cholesterol pleural effusions and are diagnostic of chylothorax even if triglycerides is not at 110 mg/dL.