QUANTIFICATION OF PLEURAL EFFUSIONS - SONOGRAPHY VERSUS RADIOGRAPHY

PURPOSE: To develop a practical method of estimating the volume of pleural effusions with sonography. MATERIALS AND METHODS: Fifty-one patients underwent sonography of the pleural space while supine. Sonographic results and results of lateral decubitus radiography were compared with actual effusion volumes. The maximum thickness of the pleural fluid layer was measured with both modalities, while actual effusion volume was determined by means of complete drainage. RESULTS: Sonographic measurements correlated statistically significantly better with actual effusion volume (r = .80) than did radiographic measurements (r = .58) (P less than or equal to .05). With sonographic measurement, an effusion width of 20 mm had a mean volume of 380 mL +/- 130 (standard deviation), while one of 40 mm had a mean volume of 1,000 mL +/- 330. Prediction error with sonographic measurement (mean, 224 mL) was statistically significantly less (P less than or equal to .002) than that with radiographic measurement (mean, 465 mL). CONCLUSION: In quantification of pleural effusions, the sonographic measurement method presented is preferable to radiographic measurement.