Segmental expansion insufficiency of the lower lobe of the right lung generally refers to the inability of the tissue of the lower lobe of the right lung to expand to the normal state, which is a manifestation of the decline in lung function; the possible causes of this symptom include pleural effusion, inflammation, lung tumor, etc. 1. Pleural effusion: the presence of pleural effusion can lead to segmental expansion of the lower lobe of the right lung. When the patient has pleural effusion, it will limit the expansion of the lungs and the movement of the thorax, resulting in lung expansion insufficiency. It can be treated by aspiration of the pleural fluid and medication to relieve it. 2. Inflammation: Inflammation of the lungs may also be the cause of right lower lobe insufficiency. Inflammatory changes in the alveoli, capillaries or interstitium of the lungs are caused by bacteria, viruses and atypical pathogens. This may lead to segmental expansion of the right lower lobe of the lung. It can be relieved by anti-infection treatment. 3. Lung tumor: patients with segmental insufficiency of the lower lobe of the right lung may also have lung tumor. This condition is relatively serious, and according to the condition, surgery, chemotherapy, radiotherapy and other timely treatments should be considered for the right lower lobe of lung insufficiency caused by lung tumor. There may be other reasons for the segmental expansion insufficiency of the lower lobe of the right lung found in chest X-ray, so it is necessary to consult the doctor in time, complete the relevant examination, make a clear diagnosis and actively cooperate with the doctor for treatment.