Volume reduction and increased density in the middle lobe of the right lung has more causes, which may be due to diseases such as pneumonia, tuberculosis or lung tumors. 1. Pneumonia: related to infection with bacteria, fungi, viruses, as well as mycoplasma and chlamydia, when the tissue of the lung lobe is repeatedly stimulated by inflammation, resulting in narrowing of the airways of the lung lobe, which reduces the volume of the middle lobe of the lung, and increased density shadows will be found through the imaging examination. 2. Tuberculosis: mainly due to long-term stimulation of Mycobacterium tuberculosis, when the bronchial mucosa appears uneven, resulting in lumen narrowing, through the examination of the middle lobe of the lungs will be found to reduce the volume, and there is a significant increase in density shadow. 3. Lung tumor: including benign and malignant tumors, when the tumor gradually increases in size and blocks the middle lobe of the lungs, the airways become narrow, and the volume of the middle lobe of the lungs will be reduced and there will be increased density shadow through examination. Reduced volume of the middle lobe of the right lung with increased density shadow may also be caused by other diseases, such as enlarged lymph nodes, bronchial dilatation and so on. If there is an abnormality through imaging, in order to exclude malignant lesions, the attending physician should be informed promptly and further lung enhancement CT and pathology biopsy analysis should be performed as prescribed by the doctor.