Differential diagnosis is very important in patients with pleural effusions. A few studies on the etiologies of massive pleural effusions have been reported, but these were conducted in different decades and locations. In the present study, the etiologic spectrum of massive pleural effusions in Korea, were evaluated through an investigation at one university hospital.

Retrospective chart reviews were performed in patients having undergone thoracentesis between July 2002 and July 2005. Pleural effusions were deemed to be massive if they occurred in two thirds or more of one hemithorax. The etiologies of massive pleural effusions, pleural fluid findings, serum laboratory findings, and sputum and pleural fluid cytologies were compared.

Of 298 pleural effusions cases, 41 (13.8%) had massive pleural effusions. The most frequent causes of massive pleural effusions were malignancy (19; 46.3%) followed by tuberculosis (15; 36.6%), parapneumonic effusion (4; 9.8%) and transudate (3; 7.3%). Compared with massive benign effusions, patients with massive malignant pleural effusions were more likely to have lower adenosine deaminase (ADA) activity, a higher amylase level and higher RBC count in their pleural fluids. Also, compared with non-tuberculosis effusions, patients with massive tuberculous pleural effusions were more likely to have lower RBC and neutrophil counts, but a higher lymphocyte count, adenosine deaminase (ADA) activity and protein level.

The most common etiologies of massive pleural effusions in Korea are malignancy and tuberculosis. A high ADA content favors a tuberculous condition, while bloody effusions with a relatively lower ADA content. favors malignancy. The proportion of tuberculosis in massive pleural effusions was higher than in previous reports.