Discriminative Role of CT in Exudative and Transudative Pleural Effusions

Abstract

by Abramowitz et al. [1] dealing with the clinical use of CT attenuation values and additional CT features in differentiating exudative and transudative pleural effusions. The authors reported that neither CT attenuation values nor additional CT features were able to discriminate exu-dative and transudative pleural effusions. In our opinion, some points in this article are not sufficiently clear.In their study, Abramowitz et al. [1] report -ed mean CT attenuation values of complicat-ed parapneumonic effusion and empyema as 8.1 ± 10.2 HU, as shown in Table 1 of their article. Although patients with empyema were included in the study, the authors did not declare the stage of the lesions. The triphasic nature of empyema, which is well established [2], consists of the exudative, transitional–fi-brinopurulent, and organizing–consolidative phases. The organizing–consolidative phase, which is defined as the presence of formal granulation tissue and protein-rich pus [3] in the pleural space, is characterized by soft-tissue density (> 20 HU) on CT [4]. A paucity of organizing–consolidative (and dominance of exudative) empyema might be the cause of the closeness of mean CT attenuation values of exudative and transudative pleural effu-sions (8.1 ± 10.2 and 10.1 ± 6.9, respectively, as shown in Table 1 of the article).Abramowitz et al. [1] revealed more frequent loculation (58% vs 36%), pleural nodules (13% vs 5%), and pleural thickening (59% vs 36%) in exudative and transudative pleural effusions, respectively,w ithouta nys tatisticallys ignificant differences between the two groups (