Pleural diagnostic techniques.

An etiologic diagnosis of a pleural effusion is made presumptively in approximately 50% of patients and definitively in an additional 25%. The cause of the effusion in the remaining patients usually is ascertained by observation with or without repeat pleural fluid analysis, specialized testing of the pleural fluid, or invasive procedures. However, a small number of patients defy a precise etiologic diagnosis even after invasive procedure. Investigators have sought various biochemical and immunologic markers in pleural fluid that would increase diagnostic certainty. Thoracoscopy, a less invasive procedure than open thoracotomy, is excellent for the diagnosis of malignancy but is of minimal benefit in the diagnosis of benign pleural disease.