The limited translucent area visible in the lower lobe of the left lung may be caused by limited pneumothorax, obstructive emphysema, compensated emphysema and so on.
1. Restricted pneumothorax: when pneumothorax occurs or in the process of absorbing pneumothorax, if there is pleural adhesion, the gas can accumulate in the localization and form a restricted pneumothorax, and the chest image manifests as a restricted translucent area visible in the lower lobe of the left lung.
2. Obstructive emphysema: this type of emphysema is caused by partial obstruction of a larger bronchial tube such as lobe, segment of the bronchus, which can be seen in endobronchial foreign body, acute pneumonia in children, early bronchial tumor and chronic inflammatory bronchial stenosis and other lesions, as a result, the distal lung tissue of the lesion is over-inflated and enlarged, resulting in the visible confined translucent area of the lower lobe of the left lung.
3. Compensatory emphysema: mostly seen in chronic tuberculosis or other chronic inflammation of the lungs, fibrosis, lobar atelectasis or resection, etc. Due to the atrophy or reduction of the lung tissue in the lesion area, compensatory emphysema occurs in the ipsilateral surviving lung tissue. The lung volume is overexpanded and a restricted translucent area is seen in the lower lobe of the left lung.