ABSTRACT
I. Introduction Pleural effusion (PE) is defined as the excessive accumulation of fluid in the pleural space indicating an imbalance between pleural fluid formation and removal. PEs are rarely a manifestation of primary pleural disease. They usually reflect a pulmonary or extrapulmonary disorder (1). Accordingly, the clinical importance of PEs arises primarily from what they really represent (infection, malignancy, heart failure, pulmonary embolism, hemothorax, or other) and secondarily from their impact on respiratory physiology.
