Thoracic ultrasonography may not be a reliable method for distinguishing transudative pleural effusions from exudative pleural effusions, according to study results published in CHEST.

Researchers retrospectively identified 285 patients who underwent a thoracic ultrasonography and a diagnostic thoracentesis with a pleural fluid analysis. A total of 300 consecutive pleural effusions were included in the analysis. The images of the pleural effusions were classified as anechoic, complex non-septated, complex septated, or complex homogenous. Diagnostic performance of the thoracic ultrasonography findings for predicting transudative vs exudative pleural effusions was assessed.

In 76% (n=229) of cases, the pleural effusions were classified as exudative. The thoracic ultrasonography demonstrated anechoic effusions in 40% (n=122) of cases, whereas 60% (n=178) of cases were identified as complex effusions. Thoracic ultrasonography images that demonstrated an anechoic appearance correlated with 56% (n=68) of cases being identified as exudative effusions vs 44% (n=54) of cases being identified as transudative effusions 54/122 (44%).

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A thoracic ultrasonography that showed a complex-appearing effusion featured a positive predictive value of 90% in terms of its ability to detect exudative effusion. Despite this finding, none of the 4 characteristics associated with thoracic ultrasonography showed high levels of specificity of a pleural diagnosis.

Limitations of the study included being conducted in a single institution as well as the lack of standardization for thoracic ultrasonography images. Additionally, some of the investigators treated the cases in this study, which may have introduced recall bias.

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The researchers added that while “the [thoracic ultrasonography] finding of a complex appearing pleural effusion strongly suggests an exudate, thoracentesis is still needed to establish a diagnosis.”

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.


Shkolnik B, Judson MA, Austin A, et al. Diagnostic accuracy of thoracic ultrasonography to differentiate transudative from exudative pleural effusion [published online March 17, 2020]. CHEST. doi:10.1016/j.chest.2020.02.051