empyema

Empyema represents infected pleural effusion with purulent fluid containing bacteria, white blood cells, and cellular debris. It most commonly develops as a complication of bacterial pneumonia (parapneumonic effusion progressing to empyema), but can also result from chest trauma, thoracic surgery, or hematogenous spread. The condition progresses through three stages: exudative (thin fluid, pH >7.30), fibrinopurulent (thicker fluid, pH <7.30, glucose <60 mg/dL), and organizing (thick, loculated fluid with fibrin deposition). Common causative organisms include Streptococcus pneumoniae, Staphylococcus aureus, and anaerobes. Clinical presentation includes fever, chest pain, dyspnea, and productive cough. Diagnosis is confirmed by thoracentesis showing purulent fluid with positive Gram stain/culture, low pH (<7.30), low glucose (<60 mg/dL), and high LDH. CT chest reveals pleural thickening and loculations. Treatment requires both antimicrobial therapy (broad-spectrum antibiotics based on culture) and drainage via thoracentesis, chest tube, or surgical intervention (VATS or thoracotomy). Complications include bronchopleural fistula, sepsis, and restrictive lung disease from pleural scarring.