Empyema is usually caused by an infection that spreads directly from the lung. It leads to a buildup of pus in the pleural space.

There can be 2 cups (1/2 liter) or more of infected fluid. This fluid puts pressure on the lungs.

Risk factors include:

• Bacterial pneumonia
• Tuberculosis
• Chest surgery
• Lung abscess
• Trauma or injury to the chest

In rare cases, empyema can occur after thoracentesis. This is a procedure in which a needle is inserted through the chest wall to remove fluid in the pleural space for medical diagnosis or treatment.

Symptoms of empyema may include any of the following:

• Chest pain, which worsens when you breathe in deeply (pleurisy)
• Dry cough
• Excessive sweating, especially night sweats
• Fever and chills
• General discomfort, uneasiness, or ill feeling (malaise)
• Shortness of breath
• Weight loss (unintentional)

Your health care provider may note decreased breath sounds or an abnormal sound (friction rub) when listening to your chest with a stethoscope (auscultation).

Tests that may be ordered include:

• Chest x-ray (may require multiple positions)
• CT scan of chest
• Thoracentesis
• Pleural fluid analysis

The goal of treatment is to cure the infection. This involves the following:

• Placing a tube in your chest to drain the pus
• Giving you antibiotics to control the infection

If you have problems breathing, you may need surgery to help your lung expand properly.

When empyema complicates pneumonia, the risk for permanent lung damage and death goes up. Long-term treatment with antibiotics and drainage are needed.

In general, most people fully recover from empyema.

Having empyema may lead to the following:

• Pleural thickening
• Reduced lung function

Contact your provider if you develop symptoms of empyema.

Prompt and effective treatment of lung infections may prevent some cases of empyema.

Empyema - pleural; Pyothorax; Pleurisy - purulent

Broaddus VC, Light RW. Pleural effusion. In: Broaddus VC, Ernst JD, King TE, et al, eds. Murray and Nadel's Textbook of Respiratory Medicine. 7th ed. Philadelphia, PA: Elsevier; 2022:chap 108.

McCool FD. Diseases of the diaphragm, chest wall, pleura, and mediastinum. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 86.

Updated by: Jatin M. Vyas, MD, PhD, Associate Professor in Medicine, Harvard Medical School; Associate in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.