A rounded low-density shadow in the upper lobe of the left lung is a description of an intrapulmonary lesion on imaging. Emphysema, pulmonary cysts, cavitary tuberculosis, and bronchiectasis are most often considered. 1. Emphysema: mainly belongs to air-containing cavities, and is related to the poor patency of the terminal fine bronchioles, and the low-density area usually has no obvious wall. 2. Lung cysts: closely related to congenital development, mainly because of the congenital development affects the patency of the terminal fine bronchial tubes, generally thin walled cysts, no inflammatory infiltration lesions in the adjacent lung tissues. 3. Cavitary tuberculosis: the wall of the cavity is wrapped by thick fibrous tissue, and the lung tissue around the cavity is often accompanied by bronchial dissemination foci, which is often dominated by fibrous hyperplasia. 4. Bronchial dilatation: cystic bronchial dilatation will also cause corresponding changes, and bronchial cartilage developmental abnormalities, the lesion is usually connected with the bronchus. Left lung upper lobe rounded low-density shadow can also be seen in other diseases, it is recommended that patients seek medical attention in time to avoid delaying the condition.