Definition of Empyema:

Empyema is a collection of pus in the space between the lung and the inner surface of the chest wall (pleural space).

Causes, incidence, and risk factors:

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

There can be a pint or more of infected fluid. This fluid puts pressure on the lungs.

Risk factors include:

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

In rare cases, empyema can occur after a needle is inserted through the chest wall to draw off fluid in the pleural space for medical diagnosis or treatment (thoracentesis).