© 2007 American Thoracic Society
Diagnosing Empyema in ChildrenTo the Editor:We read with interest the recent paper by Samatha Sonnappa and colleagues (1), which compares urokinase and video-assisted thoracoscopic surgery (VATS) for treatment of childhood empyema. This is the first randomized controlled study comparing a fibrinolytic with VATS in childhood empyema, and it brings up some points on diagnosing empyema in children that should be discussed. The authors identified and diagnosed empyema in children based on radiographic findings (i.e., pleural fluid on chest X-ray and ultrasound). Their indications for drainage were a persistent fever of 38 C° (100 F°) or greater after more than 24 h of parenteral antibiotic treatment or respiratory distress (tachypnea and/or oxygen requirement) caused by the pleural collection. Empyema is defined as the presence of pus in the pleural space. It refers to the advanced stage of parapneumonic effusion, meaning that drainage of the pleural fluid is difficult due to thick pus and the fibrin loculations in the pleural space. Although some studies performed by pediatricians have found that ultrasound is an effective method of assessing disease severity, predicting outcome, and planning treatment in children with empyema (2), there is a considerable discrepancy of findings in this matter. In a randomized trial of intrapleural urokinase therapy in children with empyema, ultrasound findings did not affect outcome (3). In addition, several authors have found that ultrasound lacks specificity in differentiating solid from cystic areas in the pleural cavity and is poor at predicting the nature of the fluid or whether or not it is infected (4). Although empyema in children usually appears as homogeneously echogenic pleural fluid on ultrasound, hemorrhagic effusion and chylothorax may have the same ultrasonic appearance (5). Echogenicity in pleural fluid is caused by cellular elements such as erythrocytes, inflammatory cells, fat droplets, or air bubbles, and ultrasound cannot differentiate between these entities (6). We believe it would be more appropriate to include patients after empyema was confirmed by macroscopic evaluation of the pleural fluid. Randomizing patients according to radiologic features may cause a significant selection bias in that many patients would resolve their parapneumonic effusion with therapeutic thoracentesis or tube thoracostomy. If this were the case, then one would not expect a randomized trial of more invasive therapies to show any differences.
Gaziantep University, Gaziantep, Turkey
Vanderbilt University, Nashville, Tennessee FOOTNOTES Conflict of Interest Statement: Neither author has a financial relationship with a commercial entity that has an interest in the subject of this manuscript. REFERENCES
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