Evaluating pleural effusions - How should you go about finding the cause?

Although many pulmonary and systemic diseases are known to cause pleural ef fusions, analysis of the pleural fluid pinpoints the cause in most cases. D istinguishing pleural transudates from exudates is an important step. Trans udate effusions are caused by a small, well-defined group of illnesses (eg, cirrhosis, congestive heart failure). Exudative effusions, on the other ha nd, are associated with a wide variety of causes, including pneumonia, mali gnancy, TB, drug-induced reactions, and many others. Some effusions remain unexplained despite extensive tests. Surgical approaches may be appropriate for some of these patients, but the risks must be carefully weighed agains t the benefits.