PLEURAL EXUDATES AND TRANSUDATES - DIAGNOSIS WITH CONTRAST-ENHANCED CT

PURPOSE: To determine the accuracy of computed tomography (CT) in enab ling differentiation of pleural exudates from transudates. MATERIALS A ND METHODS: Eighty consecutive patients (86 effusions) underwent contr ast-enhanced CT. Thoracentesis was performed to measure pleural and se rum total protein and lactate dehydrogenase (LDH) values. Effusions we re classified as exudates with accepted criteria. CT scans were evalua ted for the presence and appearance of parietal pleural and extrapleur al fat thickening. RESULTS: Fifty-nine effusions were exudates and 27 were transudates. Thirty-six of the 59 exudates (61%) were associated with parietal pleural thickening. All cases of empyema and 56% of the parapneumonic exudative effusions had pleural thickening. The specific ity of this finding in diagnosing the presence of an exudate is 96%. C ONCLUSION: Parietal pleural thickening at contrast-enhanced CT almost always indicates the presence of a pleural exudate. A pleural exudate in the absence of pleural thickening occurs most frequently in patient s with malignancy or uncomplicated parapneumonic effusion.