Pleural disease encompasses fluid accumulation in the pleural space (pleural effusion, which may be transudative, exudative, or infective), air in the pleural space (pneumothorax), and pleural thickening such as mesothelioma. Two governing principles define its behavior: the pleural space normally has no internal divisions, so air rises and fluid sinks under gravity, and the space is normally under negative pressure, which keeps the lung inflated—loss of that negative pressure via pneumothorax causes lung collapse. This is a core topic within respiratory medicine, relating to clinical examination findings, imaging, and the differential causes of fluid or air accumulation between the visceral and parietal pleura.
Pleural disease encompasses fluid accumulation in the pleural space (pleural effusion, which may be transudative, exudative, or infective), air in the pleural space (pneumothorax), and pleural thicke…