Pulmonary empyema is a collection of pus inside the pleural space. Patients will appear ill but rarely toxic. Signs and symptoms include fever, chest pain, cough, diaphoresis, chills, dyspnea, purulent sputum, anorexia, weight loss, tachycardia, pleurisy, decreased breath sounds, and friction rub. An empyema may present as a skin mass, which may ulcerate, and is caused by bacterial infection, most commonly pneumonia. It may also occur due to tuberculosis, lung abscess, chest injury, thoracentesis, thoracic surgery, abdominal infection, esophageal perforation, pneumothorax, and sepsis.

While pleural effusions more commonly arise in patients with hospital-acquired pneumonia, empyemas more commonly develop in patients with community-acquired pneumonia, typically Streptococcus pneumonia, and are commonly associated with alcohol use disorder, gastroesophageal reflux disease (GERD), and diabetes. When an empyema is associated with hospital-acquired pneumonia, it is usually methicillin-resistant Staphylococcus aureus or Pseudomonas, with S aureus being most commonly associated with thoracic surgery.

Diagnosis is made by x-ray, MRI, or CT. Less complex empyemas may be treated with nonsurgical interventions such as thoracentesis or thoracostomy while more complex empyemas with more loculations may require surgical intervention by video-assisted thoracoscopic surgery (VATS) or thoracotomy.

Additional independent risk factors for empyema development are older age or male sex (3:1 ratio in males to females). Of note, about 20% of patients who develop an empyema have diabetes or cancer.