Nodular high-density shadow in the left lower lung field and left hilar, considering pneumonia, tuberculosis or lung cancer, need to take general, therapeutic drug treatment or surgical treatment, radiotherapy and so on according to the etiology. 1. Pneumonia: It is mainly caused by inflammatory exudation and stimulation of lung tissue, and the high density will be accompanied by patchy shadow. Streptococcus pneumoniae infection can be prescribed oral benzylpenicillin, while staphylococcal infection can be oral cefixime, mycoplasma chlamydia infection can be oral azithromycin, erythromycin, clarithromycin and so on. 2. Tuberculosis: when infected with Mycobacterium tuberculosis, repeated stimulation of lung tissue may involve the left lower lobe of the lungs and the hilar, and high-density shadows in the form of dotted shadows will be found through examination. Anti-tuberculosis treatment, such as commonly used rifampicin and isoniazid, should be followed as soon as possible. 3. Lung cancer: it includes primary lung cancer and secondary lung cancer, and the examination will find a mass of high-density shadow. Early lung cancer needs radical surgery as soon as possible. If it develops into middle or late stage, radiotherapy can be considered to inhibit cancer cells, and chemotherapy drugs can be chosen such as carboplatin, etoposide, irinotecan, etc., which should be chosen according to the classification of lung cancer. Nodular high-density shadow in lung field and hilar, besides the above factors, it may also be caused by old lesions or pulmonary nodular disease, which need to be diagnosed and analyzed by imaging examination and pathological biopsy at present.