Abstract:

BACKGROUND:There are limited data examining the diagnostic accuracy of thoracic ultrasonography (TUS) in distinguishing transudative from exudative pleural effusions. RESEARCH QUESTION:What is the diagnostic accuracy of TUS in distinguishing transudative from exudative effusions in consecutive patients with pleural effusion? STUDY DESIGN AND METHODS:Consecutive patients who underwent TUS and subsequently a diagnostic thoracentesis with a pleural fluid analysis were identified. TUS images of the pleural effusions were interpreted by previously published criteria. We evaluated the diagnostic performance of TUS findings in predicting a transudative versus exudative pleural effusions as well as specific pleural diagnoses. RESULTS:We evaluated 300 consecutive pleural effusions in 285 patients. The pleural effusions were classified as exudative in 229/300 (76%) cases. TUS showed anechoic effusions in 122/300 (40%) cases and complex effusions in 178/300 (60%) cases. An anechoic appearance on TUS was associated with exudative effusions 68/122 (56%) as compared to transudative effusions 54/122 (44%). The presence of a complex-appearing effusion on TUS was highly predictive of and exudative effusion (positive predictive value of 90%). However, none of the four TUS characteristics were highly specific of a pleural diagnosis. INTERPRETATION:Thoracic ultrasonography is inadequate to reliably diagnose a transudative pleural effusion. Although the TUS findings of a complex effusion may suggest an exudative pleural effusion, specific pleural diagnoses cannot be confidently predicted.