Curr Respir Care Rep (2014) 3:52–60 DOI 10.1007/s13665-014-0074-4
PLEURAL DISEASES AND MESOTHELIOMA (G LEE, SECTION EDITOR)
Parapneumonic effusions: epidemiology and predictors of pleural infection Simon Finch & James D. Chalmers
Published online: 28 March 2014 # Springer Science+Business Media New York 2014
Abstract The development of a pleural effusion represents a common complication of pneumonia. Clinically there is a recognised spectrum of effusions from simple parapneumonic, which typically resolve without requiring intervention other than antibiotic treatment, to complicated parapneumonic effusions associated with bacterial infection and inflammatory cell infiltration, through to empyema, with the presence of frank pus in the pleural space. It was previously believed that no clinical features could identify patients at risk of pleural infection, but recent research suggests this is not the case. Patients with pleural infection after pneumonia are younger, more frequently have a history of alcohol or substance abuse, and have evidence of marked systemic inflammation, with higher levels of C-reactive protein, leucocyte counts and platelet counts compared to patients with pneumonia who do not develop pleural complications. Intriguingly, patients with chronic obstructive pulmonary disease have a low risk of pleural infection, despite a high frequency of pneumonia, and it has been speculated that bacterial colonisation or inhaled corticosteroids may play a protective role in these patients. This review summarises the data on the incidence and clinical predictors of pleural infection in patients with pneumonia, and considers the implications of these risk factors for management and what we know of the pathophysiology of parapneumonic effusions.
Keywords Pneumonia . Empyema . Pleural effusion . Inflammation . Severity . Mortality
S. Finch : J. D. Chalmers (*) Tayside Respiratory Research Group, University of Dundee, Dundee DD1 9SY, Scotland e-mail:
[email protected]
Introduction Pleural effusion represents a common complication of community-acquired pneumonia. While the incidence depends to some extent on the imaging modality used, frequencies of up to 57 % of patients with community-acquired pneumonia are reported to have detectable pleural fluid [1–3]. The clinical classification of parapneumonic effusions identifies three groups with a distinct prognosis [3, 4]. First, there is the simple or uncomplicated parapneumonic effusion, which should resolve with appropriate antibiotic therapy without any consequences within the pleural space. Second, there is a complicated parapneumonic effusion denoting the presence of bacterial infection in the pleural space with an associated inflammatory response. A complicated effusion requires pleural drainage to resolve and without treatment may progress to an empyema. Finally, an empyema represents frank pus in the pleural space and requires pleural drainage and may also require surgical treatment [3]. Parapneumonic effusions are classified on the basis of biochemical criteria, appearance and microbiology (Table 1) [3]. Lights criteria for defining complicated parapneumonic effusions include a pH
