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Epidemiology; clinical presentation; and evaluation of parapneumonic effusion and empyema in children

Ibrahim A Janahi, MD
Khoulood Fakhoury, MD
Section Editors
Gregory Redding, MD
Sheldon L Kaplan, MD
Deputy Editor
Alison G Hoppin, MD


Simple parapneumonic effusion is defined as pleural effusion associated with lung infection (ie, pneumonia). These effusions result from the spread of inflammation and infection to the pleura. Much less commonly, infections in other adjacent areas (eg, retropharyngeal, vertebral, abdominal, and retroperitoneal spaces) may spread to the pleura resulting in the development of effusion. Parapneumonic effusions or empyema affect 2 to 12 percent of children with pneumonia, and up to 28 percent of those requiring hospitalization [1,2].

Early in the course of parapneumonic effusion, the pleura becomes inflamed; subsequent leakage of proteins, fluid, and leukocytes into the pleural space forms the effusion. At the time of formation, the pleural effusion is usually sterile with a low leukocyte count. With time, bacteria invade the fluid, resulting in empyema, which is defined as the presence of grossly purulent fluid in the pleural cavity. The development of pleural empyema is determined by a balance between host resistance, bacterial virulence, and timing of presentation for medical treatment [3].

The epidemiology, etiology, pathophysiology, clinical presentation, and evaluation of parapneumonic effusion and empyema in children will be reviewed here. The management of parapneumonic effusion and empyema in children is discussed separately. (See "Management and prognosis of parapneumonic effusion and empyema in children".)

The evaluation and management of parapneumonic effusion in adults also are discussed separately. (See "Diagnostic evaluation of a pleural effusion in adults: Initial testing" and "Imaging of pleural effusions in adults" and "Parapneumonic effusion and empyema in adults".).


Between 1962 and 1980, empyema was reported to occur in approximately 0.6 percent of children with bacterial pneumonia, despite early diagnosis and treatment [4]. However, the number of children with complicated pneumonia appears to be increasing, and effusion now occurs in about 2 to 12 percent of community-acquired pneumonia in Europe and the United States [1,2,5]. In children younger than two years of age, pneumonia hospitalizations complicated by empyema increased twofold from 3.5 cases per 100,000 children in 1996 through 1998 to 7.0 cases per 100,000 children in 2005 through 2007 [6]. Rates of pneumococcal and streptococcal empyema remained stable, whereas rates of staphylococcal and other or unspecified empyema increased 4.08- and 1.89-fold, respectively. Similarly in patients two to four years of age, the rate of pneumonia complicated by empyema almost tripled from 3.7 to 10.3/100,000 with 2.17, 2.80, 3.76, and 3.09-fold increases in rates of pneumococcal, streptococcal, staphylococcal, and other or unspecified empyema, respectively. Similar increases have been seen in the United Kingdom [7-9], and Scandinavia [10].

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Literature review current through: Sep 2017. | This topic last updated: Apr 28, 2017.
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