Noninvasive evaluation of the patient with a pleural effusion

Pleural fluid formation is an indicator of a pathologic process that may be of primary pulmonary origin but also may be a reflection of disease in virtually any other organ system or a systemic disease. A thoracentesis should be performed on any patient in whom the cause of the effusion has not been established yet. The possible exception to this is an effusion thought to be secondary to uncomplicated congestive heart failure. The presumptive or definitive diagnosis can be established in 75% of patients by following patient history, physical examination, and pleural fluid analysis.