Value of sonography in determining the nature of pleural effusion: analysis of 320 cases.

Abstract

To assess the value of sonography in determining the nature of pleural effusions, we prospectively analyzed the sonographic findings in 320 patients with pleural effusion of various causes (224 with exudates and 96 with transudates). The nature of the effusions was established on the basis of chemical, bacteriologic, and cytologic examination of pleural fluid; pleural biopsy; and clinical follow-up. All patients had high-frequency, real-time sonography performed by one of three sonographers who had no clinical information concerning the patients. The sonographer evaluated the images for internal echogenicity of the effusion, thickness of the pleura, and associated parenchymal lesions of the lung. The images were also printed out and interpreted a second time by the other two sonographers to reach a consensus. Our results showed that the two types of effusions could be distinguished on the basis of sonographic findings. Transudates were anechoic, whereas an anechoic effusion could be either a transudate or...