Empyema is a collection of pus in the cavity between the lung and the membrane that surrounds it (pleural space).

Empyema is caused by an infection that spreads from the lung and leads to an accumulation of pus in the pleural space. The infected fluid can build up to a quantity of a pint or more, which puts pressure on the lungs, causing shortness of breath and pain.

Risk factors include recent pulmonary (lung) conditions including bacterial pneumonia, lung abscess, thoracic surgery, trauma or injury to the chest, or rarely, a needle inserted through the chest wall to draw off fluid in the pleural space (thoracentesis).

• Dry cough
• Fever and chills
• Excessive sweating, especially night sweats
• General discomfort, uneasiness, or ill feeling (malaise)
• Unintentional weight loss
• Chest pain, which worsens on deep inhalation (inspiration)

The health care provider may note abnormal findings, such as decreased breath sounds or a friction rub, when listening to the chest with a stethoscope (auscultation).

Tests may include the following:

• Chest x-ray
• Thoracentesis
• Pleural fluid gram stain and culture
• CT scan of chest