The patchy high-density shadow in the upper lobe of the left lung needs to be judged based on the patient’s clinical manifestations, specific description of chest imaging, and objective ancillary examinations. The patchy shadow in the upper lobe of the left lung mostly indicates the possibility of pneumonia or tuberculosis. If it is pneumonia, cough, sputum, high fever, or even blood in the sputum may appear. Blood tests may indicate an increase in total leukocytes and neutrophils, and calcitoninogen and C-reactive protein may also be increased, and CT may specifically describe the size of the pneumonia. In the case of tuberculosis changes seen in the apical and posterior segments of the upper lobe and the dorsal segment of the lower lobe, clinical symptoms of tuberculosis toxicity such as dry cough, low sputum, hot flashes, night sweats, or even blood in the sputum and progressive body wasting may occur. Blood count may indicate mononuclear or lymphocytosis, and chest CT may indicate patchy changes in the upper lobe with polymorphic changes such as nodules, proliferation, calcification, fibers and cords. Therefore, the presence of a patchy high-density shadow in the upper lobe of the left lung requires a comprehensive judgment of whether it is likely to be tuberculosis or pneumonia.