Biochemical and cytologic characteristics of pleural effusions secondary to pulmonary embolism.

STUDY OBJECTIVES: To characterize the biochemical and cytologic constituents of pleural effusions secondary to pulmonary embolism.

DESIGN: A descriptive clinical study.

SETTING: A community teaching hospital with 750 beds, which acts as a tertiary referral center for several subspecialties.

PATIENTS AND INTERVENTIONS: Patients with pleural effusions secondary to pulmonary embolism who underwent diagnostic thoracentesis during the last 7 years were retrospectively studied. Pleural fluid mesothelial hyperplasia was revised and compared with that found in patients with pleural effusions of different origin.

RESULTS: Pleural effusions from all 60 patients with pulmonary embolism were exudates, and in 40 patients (67%) contained erythrocyte counts > 10,000/microL. A bloody appearance was not related to the use of anticoagulant therapy before thoracentesis. Polymorphonuclear leukocytes were predominant in 36 patients (60%); in 11 patients (18%), a proportion of eosinophils > 10% was found. Mesothelial hyperplasia was significantly higher in patients with pulmonary embolism than in patients in the control group (p < 0.01).

CONCLUSIONS: In the absence of trauma, a bloody or eosinophilic effusion with a marked mesothelial hyperplasia should prompt a workup to rule out embolism. The finding of transudative pleural fluid chemistries in these patients should not be assumed to be secondary to embolism before ruling out other causes of transudative effusion.