ABSTRACT
The initial step in evaluating pleural effusions of uncertain etiology is the performance of thoracentesis with the classification of pleural fluid as exudates or transudates (1). The presence of an exudative effusion presents a wide differential diagnosis of various inflammatory and malignant conditions, which usually warrants additional diagnostic testing. Conversely, the presence of a transudative effusion may limit the need for further clinical evaluation because these effusions are often attributable to clinically apparent conditions, such as congestive heart failure, cirrhosis with ascites, or nephrosis. Accurate classification of effusions, therefore, is fundamentally important in managing patients with pleural disease. This chapter will review existing approaches for discriminating between exudative and transudative effusions and critically appraise the evidence supporting the diagnostic accuracy of each approach.
