左下胸膜表面可看见黄褐色脓性渗出物。肺炎也可能并发胸膜炎。最初,可能有胸膜腔渗出，也可能出现纤维素性胸膜炎。然而,细菌感染传播到胸膜，并形成脓性胸膜炎，胸膜腔内脓液聚集形成脓胸。
The pleural surface at the lower left demonstrates areas of yellow-tan purulent exudate. Pneumonia may be complicated by a pleuritis. Initially, there may just be an effusion into the pleural space. There may also be a fibrinous pleuritis. However, bacterial infections of lung can spread to the pleura to produce a purulent pleuritis. A collection of pus in the pleural space is known as empyema.
