Pleuritis and pleural effusions.

A variety of diseases either directly or indirectly affect the pleura, resulting in the accumulation of pleural fluid. A pleural effusion develops whenever the influx of fluid into the pleural space is greater than the efflux. It is now clear that the parietal pleura has the primary role in the reabsorption of pleural fluid normally and during pathologic conditions. Recently, models of experimental pleuritis have demonstrated the importance of inflammatory cytokines in the pathogenesis of both asbestos- and endotoxin-induced pleural effusions.