Journal Article

A Simple Method for Differentiating Complicated Parapneumonic Effusion/Empyema from Parapneumonic Effusion Using the Split Pleura Sign and the Amount of Pleural Effusion on Thoracic CT

Ishii, Haruyuki, Takizawa, Hajime, Tsukahara, Yayoi, Light, Richard W., Koide, Takashi, Goto, Hajime, Kurai, Daisuke, Saraya, Takeshi, Kimura, Hirokazu, Tsujimoto, Naoki

2015

Overview

Pleural separation, the \"split pleura\" sign, has been reported in patients with empyema. However, the diagnostic yield of the split pleura sign for complicated parapneumonic effusion (CPPE)/empyema and its utility for differentiating CPPE/empyema from parapneumonic effusion (PPE) remains unclear. This differentiation is important because CPPE/empyema patients need thoracic drainage. In this regard, the aim of this study was to develop a simple method to distinguish CPPE/empyema from PPE using computed tomography (CT) focusing on the split pleura sign, fluid attenuation values (HU: Hounsfield units), and amount of fluid collection measured on thoracic CT prior to diagnostic thoracentesis. A total of 83 consecutive patients who underwent chest CT and were diagnosed with CPPE (n=18)/empyema (n=18) or PPE (n=47) based on the diagnostic thoracentesis were retrospectively analyzed. On univariate analysis, the split pleura sign (odds ratio (OR), 12.1; p<0.001), total amount of pleural effusion (≥30 mm) (OR, 6.13; p<0.001), HU value≥10 (OR, 5.94; p=0.001), and the presence of septum (OR, 6.43; p=0.018), atelectasis (OR, 6.83; p=0.002), or air (OR, 9.90; p=0.002) in pleural fluid were significantly higher in the CPPE/empyema group than in the PPE group. On multivariate analysis, only the split pleura sign (hazard ratio (HR), 6.70; 95% confidence interval (CI), 1.91-23.5; p=0.003) and total amount of pleural effusion (≥30 mm) on thoracic CT (HR, 7.48; 95%CI, 1.76-31.8; p=0.006) were risk factors for empyema. Sensitivity, specificity, positive predictive value, and negative predictive value of the presence of both split pleura sign and total amount of pleural effusion (≥30 mm) on thoracic CT for CPPE/empyema were 79.4%, 80.9%, 75%, and 84.4%, respectively, with an area under the curve of 0.801 on receiver operating characteristic curve analysis. This study showed a high diagnostic yield of the split pleura sign and total amount of pleural fluid (≥30 mm) on thoracic CT that is useful and simple for discriminating between CPPE/empyema and PPE prior to diagnostic thoracentesis.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Aged / Aged, 80 and over / Atelectasis / Attenuation / CAT scans / Computed tomography / Confidence intervals / Diagnosis, Differential / Diagnostic systems / Empyema / Empyema, Pleural - complications / Empyema, Pleural - diagnostic imaging / Female / Health aspects / Humans / Male / Medical diagnosis / Methods / Middle Aged / Multivariate analysis / Patients / Pleura / Pleura - diagnostic imaging / Pleura - pathology / Pleural effusion / Pleural Effusion - complications / Pleural Effusion - diagnostic imaging / Pleural fluid / Pneumonia - diagnostic imaging / Pneumonia - etiology / Radiography, Thoracic - methods / Retrospective Studies / Risk analysis / Risk factors / ROC Curve / Septum / Thorax / Tomography, X-Ray Computed - methods