A small nodular high-density shadow in the lower lobe of the left lung is a description of an intrapulmonary nodule on lung imaging, which is mostly considered to be an intrapulmonary fibrous foci, intrapulmonary lymph nodes, intrapulmonary tuberculous foci, and intrapulmonary tumors, and so on. 1. Intrapulmonary fibrous foci: they are the residue of inflammation after absorption, and are similar to scarring in the lungs. 2. Intrapulmonary lymph nodes: most of them are located in the subpleural or interlobular parietal pleura, which are enlarged by inflammation stimulation, and some of them can be resorbed. 3. Tuberculosis foci in the lungs: If there is tuberculosis in the lungs, and caseous granulation tissue appears, there will also be this manifestation. 4. Intrapulmonary tumor: Early primary lung cancer will have corresponding changes, usually the nodules are irregular in shape and can be seen as burrs or lobes. Nodular high-density shadow in the lower lobe of the left lung can also be seen in other diseases, and it is recommended that the patient should consult the doctor in time so as to avoid delaying the condition.