Patchy hyperdense shadow in the upper lobe of the left lung is generally considered to be an infectious disease such as pneumonia or tuberculosis, or it may be a non-infectious disease such as allergy or lung tumor, which requires a comprehensive diagnosis by the patient’s chest imaging, clinical manifestations, and auxiliary examinations. 1. If it is pneumonia, routine blood test shows increased neutrophils and total white blood cells, C-reactive protein and calcitoninogen are also increased, and chest CT can indicate the size of pneumonia. Most of the patients have cough, high fever, coughing up sputum and blood in sputum. Intravenous antibiotics are chosen for treatment, such as quinolones, cephalosporins and other antibiotics. 2. In case of tuberculosis, routine blood test shows increased lymphocytes or mononuclear, and chest CT can indicate patchy changes in the upper lobes, and cause polymorphic changes such as proliferation, nodules, fibers, calcification, cords and so on. The changes are seen in the apical, posterior and dorsal segments of the upper lobe, and patients usually have symptoms of tuberculosis toxicity such as low sputum, dry cough, blood in sputum, night sweats, hot flashes, and lethargy. Anti-TB drugs are chosen for anti-TB treatment. 3. If non-infectious diseases such as allergies and lung tumors are considered, the shadows in the upper lobe of the left lung will only be absorbed if they are treated for the cause of the disease. It is recommended to consult a doctor in time for further improvement and further examination to clarify the cause of the disease for causative treatment.