Unexpandable lung is present when the lung is unable to expand to the chest wall and achieve visceral and parietal pleural apposition [1,2]. Full expansion of the lung can be prevented by inflammatory or fibrotic processes affecting the visceral pleura or by extrapleural processes such as endobronchial obstruction, chronic lung atelectasis, or lung parenchymal fibrosis .
Unexpandable lung caused by disease of the visceral pleura usually comes to medical attention when removal of pleural fluid does not result in lung reexpansion or during the evaluation of a pleural effusion of undetermined etiology.
The two types of pleural disease that result in unexpandable lung are lung entrapment and trapped lung. The diagnosis and management of these conditions will be reviewed here. The evaluation of pleural effusions, including those of undetermined etiology, the measurement of pleural pressures, and the physiology of excess pleural fluid production and accumulation are discussed separately. (See "Diagnostic evaluation of a pleural effusion in adults: Initial testing" and "Diagnostic evaluation of pleural effusion in adults: Additional tests for undetermined etiology" and "Diagnostic thoracentesis" and "Measurement of pleural pressure" and "Mechanisms of pleural liquid accumulation in disease".)
The two types of pleural disease that result in unexpandable lung are lung entrapment and trapped lung. Both of these processes are associated with the presence of pleural fluid.
●In lung entrapment, the lung is unexpandable due to visceral pleural restriction from active pleural disease, such as malignancy or infection.