Pleural effusions in right-sided endocarditis: characteristics and pathophysiology

The incidence, characteristics, and pathogenesis of pleural effusions in patients with right-sided endocarditis (RSE) are poorly defined. We have recently observed four patients with a history of intravenous drug abuse and bacteremia due to Staphylococcus aureus who had pleural effusions during an episode of RSE. We report the pleural fluid characteristics of five effusions in these four patients and attempt to define the pathogenesis of each. We found that (1) an exudative, sterile, serosanguineous, or bloody effusion is common in RSE, (2) empyema occurred in only one patient, and (3) transudative effusions due to CHF were not observed. Possible mechanisms of pleural fluid formation in RSE include parapneumonic effusion, septic pulmonary emboli with or without infarction, and empyema. Congestive heart failure does not appear to be a common cause of pleural effusion in pure right-sided endocarditis.