An empyema is an infection in fluid that can build up around the lung. There are three phases of empyema:
- Phase one, the exudative phase, all the fluid around the lung is liquid and easily drained.
- Phase two, the fibrinopurulent stage, the fluid has a gelatinous component due to fibrin and develops pockets.
Phase three, the fluid becomes thick and a ring forms around it and on the lung.