Differential diagnosis of pleural effusions

Abstract

A variety of disease states are associated with the development of pleural effusions, which sometimes makes the differential diagnosis problematic. Pleural effusions can be classified into two categories, transudative and exudative, based on the characteristics of the pleural fluid. While transudative effusions are the result of changes in hydrostatic or oncotic pressure with no pathological change in the structure of the pleural membrane or condition of the vascular wall, exudative effusions collect in the pleural cavity as a result of pathological changes or structural breakdown of the pleura. In recent years, Light's diagnostic criteria have been most commonly used to differentiate between these two categories of pleural effusion and to help delineate the underlying cause, including malignant tumors, infectious diseases (such as tuberculosis), collagen vascular disease, liver disease, pancreatic disease, iatrogenic causes, and gynecological diseases. Pleural mesothelioma secondary to asbestos exposure has been recognized as a cause of pleural effusion, but diagnostic confirmation is difficult in some cases. When pleural effusion cannot be controlled despite treatment of the underlying cause, pleurodesis can be performed as a potentially permanent method of treatment.