If the nodular shadow in the dorsal segment of the lower lobe of the right lung is caused by tuberculosis and pneumonia, it is usually not serious, if it is a malignant tumor of the lung, it is more serious. 1. Tuberculosis: mainly due to the infection of tuberculosis bacillus in lung tissue, the disease is generally not serious, timely treatment can be cured, but the course of the disease is relatively long, and need to take long-term medication. The disease is usually not serious and can be cured by timely treatment, but the course of the disease is long and requires long-term medication. If it is persistent tuberculosis or refractory tuberculosis, it is more serious. 2. Pneumonia: mainly due to bacterial, viral or fungal infections, which can be cured after timely treatment and will not leave complications, and is generally not serious. 3. Malignant tumor of lung: malignant tumor of lung is more serious, if it is in the early stage, after surgery and application of radiotherapy can get a better prognosis; if it belongs to the middle stage or late stage, the condition is relatively serious, obviously affecting the quality of life, and life is in danger. If you only find out that there is a nodular shadow in the dorsal segment of the lower lobe of the right lung, you need to consult a doctor in time, under the guidance of a professional doctor to carry out the corresponding examination, puncture biopsy to clarify the benignity and malignancy of the lesion, and then targeted treatment.