Diagnostic Accuracy of Thoracic Ultrasonography to Differentiate Transudative From Exudative Pleural Effusion

Chest. 2020 Aug;158(2):692-697. doi: 10.1016/j.chest.2020.02.051. Epub 2020 Mar 17.


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 vs exudative pleural effusions and specific pleural diagnoses.

Results: We evaluated 300 consecutive pleural effusions in 285 patients. The pleural effusions were classified as exudative in 229 of 300 cases (76%). TUS showed anechoic effusions in 122 of 300 cases (40%) and complex effusions in 178 of 300 cases (60%). An anechoic appearance on TUS was associated with exudative effusions (68/122; 56%) as compared with transudative effusions (54/122; 44%). The presence of a complex-appearing effusion on TUS was highly predictive of an 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 diagnose a transudative pleural effusion reliably. Although the TUS findings of a complex effusion may suggest an exudative pleural effusion, specific pleural diagnoses cannot be predicted confidently.

Keywords: diagnosis; exudate; pleural effusion; thoracic ultrasonography; transudate.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Diagnosis, Differential
  • Exudates and Transudates / diagnostic imaging*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Pleural Effusion / diagnostic imaging*
  • Thoracentesis
  • Ultrasonography / methods*
  • Ultrasonography, Interventional