To evaluate exudative pleural fluid, thoracentesis for microbiological and cytological examination and pleural biopsy by using a Cope needle are traditionally performed. Even after these studies, about 20% of patients remain undiagnosed. We evaluated the diagnostic accuracy and complications of 2-mm minithoracoscopy instead of blind biopsy in patients with undiagnosed exudative pleural effusion.

Fifteen patients with exudative pleural effusion underwent thoracoscopy between April 2002 and August 2003. The indication was undiagnosed pleural effusions after having performed sputum and pleural fluid examinations both microbiologically and cytologically.

The median age of the patients was 56 years (range 21-77). Pleural effusions were lymphocyte-dominant in 11 patients (73.3%) and neutrophil-dominant in 3 (20.0%). The remaining patient (6.7%) had pleural-fluid eosinophilia. Minithoracoscopic biopsy revealed accurate diagnosis in 14 patients (93.3%), consisting of tuberculous pleurisy in 8 (66.7%), malignant effusions in 4 (33.3%), and parapneumonic effusions in 2 (13.3%). One was diagnosed as having paragonimiasis from thoracoscopic findings and clinical considerations. There was no procedure-associated mortality. There were six cases of new onset fever (40%) and one of pneumothorax (6.7 %).

Two-millimeter minithoracoscopy, which is less invasive than conventional thoracoscopy, was an accurate and safe method for undiagnosed exudative pleural effusion.