Pleural effusions due to pulmonary embolism.

PURPOSE OF REVIEW: The review highlights both the radiographic and the fluid characteristics of pleural effusions occurring in patients with pulmonary embolism.

RECENT FINDINGS: Recent data show that one third of patients with pulmonary embolism have pleural effusions as demonstrated by chest radiograph. By using computed tomography or ultrasonography, pleural effusions have been observed in half of these patients. The effusions occupy one third or less of the hemithorax in 90% of the patients and are unilateral in more than three quarters of them (even if computed tomography is the reference technique). On computed tomography, about 20% of pleural effusions show loculations, which is true particularly in those patients with a delayed diagnosis. Although previously thought to be transudates on occasion, two recent series found that all of the effusions are exudates.

SUMMARY: Pleural effusions associated with pulmonary embolism are usually small, unilateral and exudative when analyzed. If the diagnosis of pulmonary embolism is delayed, the effusion may become loculated.