Long-term Outcome of Patients With Undiagnosed Pleural Effusion.

INTRODUCTION The cause of exudative pleural effusion cannot be determined in some patients. The longterm outcomes of patients with undiagnosed pleural effusion were analyzed. METHODS Patients with exudative pleural effusion whose diagnostic procedures included pleural biopsy using video-assisted thoracoscopic surgery carried out between 2008 and 2012 were evaluated retrospectively. Patients diagnosed with non-specific pleuritis were included. Fifty-three patients with available follow-up data were included in the study. RESULTS Forty men and 13 women (mean age 53.9±13.9 years) were included. Median follow-up time was 24 months. No diagnosis was given in 27 patients (51%), and a clinical diagnosis was given in 26 patients (49%) during the follow-up period. Malignant disease (malignant mesothelioma) was diagnosed in 2 (3.7%) patients. Other diseases were parapneumonic effusion in 12, congestive heart failure in 8, and miscellaneous in 4 patients. Volume of effusion at the time of initial examination and re-accumulation of fluid after video-assisted thoracoscopic surgery were associated with malignant disease (P=.004 and .0001, respectively). CONCLUSION Although the probability is low, some patients with exudative pleural effusion undiagnosed after pleural biopsy via video-assisted thoracoscopic surgery may have malignant disease. Patients with an initially large volume of effusion that re-accumulates after examination should be closely monitored.