Pneumonia can be complicated by the development of a parapneumonic effusion, which has increased morbidity and mortality. Complicated parapneumonic effusion and empyema often necessitate prolonged treatment, longer hospital stay and interventions. Parapneumonic effusions arise from inflammation in the lungs and pleural space from a cascade of inflammatory events including, direct invasion of bacteria and bacteriology virulence features. Patient factors and comorbid illnesses such as heart failure also contribute to the pathophysiology of parapneumonic effusion development.
The evolution of parapneumonic effusions can be divided into three progressive stages: (I) exudative; (II) fibrinopurulent; and (III) organizing stages. These stages can help categorize effusions into groups in order to evaluate risk of an uncomplicated or complicated course requiring intervention. Clinical data should be collected to classify patients and a stepwise approach be taken in the management.