The causes of vesicular low density shadow in the middle lobe of the right lung include pulmonary alveolus, emphysema and pulmonary cyst. 1. Pulmonary alveolus: Chest CT of patients with pulmonary alveolus can be manifested as cystic low-density shadow in the lung lobe, which is often secondary to inflammatory lesions in the small bronchial tubes, manifesting chest tightness and shortness of breath, and spontaneous pneumothorax can occur. 2. Emphysema: patients with emphysema may have cystic low-density shadow on imaging, mostly caused by prolonged smoking, and some patients are related to environment and heredity, etc., and may have poor respiration, shortness of breath, etc., and in severe cases, they may have chronic respiratory failure or even pulmonary heart disease. 3. Pulmonary cysts: patients with pulmonary cysts can appear in the lungs vesicular low-density shadow, the volume of small pulmonary cysts, patients can be asymptomatic, the volume of large pulmonary cysts, the lung tissue will produce pressure, affecting breathing. Patients usually have discomfort, timely to the hospital, do not be careless, so as not to delay treatment.