Pleural effusions.

There are many diseases that cause pleural effusions. When a patient with a pleural effusion is first evaluated, one should determine if the patient has a transudate or an exudate. A diagnostic approach to the patient with an undiagnosed pleural effusion is outlined. The most common pleural effusions including those caused by congestive heart failure, cirrhosis, pneumonia, malignancy, tuberculosis, lupus erythematosus, rheumatoid disease, and chylothorax are discussed.