1, lesions in the pulmonary artery itself: congenital heart disease with shunts, connective tissue disease, AIDS, liver disease (portal hypertension), thyroid disease, post-splenectomy, etc.; 2, diseases causing increased pulmonary venous pressure: valvular disease, cardiomyopathy and constrictive pericarditis, etc.; 3, lung and or thoracic diseases: chronic obstructive pulmonary disease, interstitial lung disease, sleep apnea, thoracic deformity, etc.; 4, diseases causing local blockage of the pulmonary artery: pulmonary thromboembolism, lung tumors, schistosomiasis, etc.; 5, other diseases: nodular disease, etc.