The hilum is composed of the main bronchial tubes, nerves, lymphatic vessels as well as pulmonary arteries and veins, etc. Enlargement of the hilum is often considered as a respiratory disease, circulatory system disease, tumor-occupying disease, etc. 1. Respiratory system diseases: such as bronchitis and pneumonia caused by bacteria and viruses, the airways, nerves and blood vessels in the hilum are stimulated by inflammation, and the hilum will enlarge. 2. Circulatory system diseases: such as congenital heart disease, high pressure in the pulmonary circulation, manifested by vascular enlargement of the hilar shadow. 3. Tumor-occupying disease: lymph node metastasis caused by lung cancer can lead to hilar enlargement, and lymphoma of pulmonary artery hypertension are also some common factors leading to hilar enlargement. There are other causes of hilar enlargement, so it is suggested that patients should go to regular hospitals in time to clarify the cause of the disease and take active treatment.