Empyema

Empyema discusses the clinical features, evolution, differential diagnosis, complications, and imaging manifestations of this disease process. There are three distinct stages in the evolution of empyema: exudative stage, fibropurulent stage, and organizing stage. The majority of patients with empyema are symptomatic and present with cough, fever, chest pain, and dyspnea. A simple parapneumonic effusion manifests as a free small to moderate pleural effusion of variable size and is usually associated with adjacent consolidation. Empyema manifests as a loculated pleural effusion which may or may not be associated with adjacent consolidation. Empyema typically exhibits smooth parietal pleural thickening and enhancement indicative of an exudative pleural effusion. Approximately 50% exhibit the split pleural sign with thickening and enhancement of the visceral and parietal pleura. Complications of empyema include bronchopleural fistula, empyema necessitans, “trapped” lung, and malignant transformation. The treatment of empyema is drainage via thoracostomy tubes or surgical decortication in complicated cases.