4/2007Approach to the patient with pleural effusion

TOMASZ J. KUŹNIAR (Division of Pulmonary and Critical Care Medicine, Evanston Northwestern Healthcare,Evanston, IL, USA; Division chair: Daniel W. Ray, M.D.)

Summary
Pleural effusion is a common clinical symptom in primary care. In most cases, thoracentesis is indicated to sample the fluid and determine its etiology. Based on the pleural fluid analysis, it can be classified as ei- ther an exudate or a transudate. This clinically useful distinction is most commonly established based on the set of three criteria known as Light’s criteria. Most recently, more complex but clinically useful methods have been applied to determine odds ratios of the fluid being an exudate or a transudate. Vast majority of transudative pleural effusions result from five processes: congestive heart failure, liver disease, atelectasis, nephrotic syndrome, and pulmonary embolism. On the other hand, the differential of an exudative fluid encompasses a long list of inflammatory, infectious, neoplastic, drug- and procedure-related etiologies. Specific characteristics of pleural effusion, such as presence of blood, eosinophils, or chylomicrones may allow to establish the diagnosis; in some cases aggressive workup with pleural sampling is necessary.

Key words: pleural effusion, transudate, exudate