Pleural Fluid Echogenicity Measured by Ultrasound Image Pixel Density to Differentiate Transudative versus Exudative Pleural Effusions

More than 1.5 million patients are diagnosed with a pleural effusion annually in the United States (1). Pointofcare ultrasound is commonly used to categorize pleural effusions radiologically as simple, complex septated, complex nonseptated, or homogeneously echogenic; however, the utility of ultrasound to differentiate transudative versus exudative pleural effusions is less clear. Certain sonographic features, including septations, loculations, and fibrinous stranding, have been associated with exudative pleural effusions (2, 3), but conflicting reports exist on whether exudates have increased fluid echogenicity (2, 4). The researchers hypothesize that combining quantitative measurement of pleural fluid echogenicity and qualitative characteristics can improve identification of exudates and guide decisions about drainage. This exploratory study evaluated the utility of measuring pleural fluid echogenicity quantitatively using computerized image pixel density to differentiate transudative versus exudative pleural effusions. A retrospective observational study was conducted at the University County Teaching Hospital and Veterans Hospital in subjects with thoracentesis between January 2012 and December 2015. The Institutional Review Board (HSC20120034H) has approved this study.