Which condition is identified as an infected pleural effusion?

Empyema is defined as the accumulation of pus within the pleural cavity, which occurs as a result of infection. This condition arises when an infection such as pneumonia, tuberculosis, or any other thoracic infection leads to inflammation and subsequent differentiation of the pleural fluid into infected and non-infected components. As bacteria proliferate in the pleural space, this typically results in a thick, turbid fluid collection, which characterizes empyema.

In contrast, pneumothorax involves the presence of air in the pleural space, leading to potential lung collapse but is not a result of infectious processes. Hydrothorax refers to the accumulation of sterile fluid in the pleural cavity, often due to non-infectious conditions such as heart failure or cirrhosis, while hemothorax involves blood in the pleural space due to trauma or malignancy, not caused by infection. Understanding these distinctions is crucial for identification and appropriate management of pleural conditions.