Empyema is an infection of the chest cavity, characterized by pus in the space between the lung and rib cage. Empyemas can develop for several reasons; complications of pneuomonia are the most common. Trauma to the chest with bleeding into the pleural cavity can also lead to an empyema.

Treatment of empyema usually requires surgery to drain the pus and remove any scar tissue which has formed. If an empyema is not treated early, scarring of the pleura can occur, which can lead to portions of the lung being damaged and trapped. This can require a much more extensive surgery for repair.