Empyema is an infection in which pus develops in your pleural space.

Pus is a thick, discolored (white, yellow, pink or green) fluid that your body creates to help fight infection. It consists of white blood cells, dead tissue and bacteria.

Your pleural space is a hollow area (cavity) between your lungs and underneath your chest wall.

Without proper treatment, empyema can get worse and may be fatal. If you have symptoms of empyema, call a healthcare provider right away.