Solidation of the lung is a condition in which the alveolar lumen accumulates plasma, fibrin, and cellular components for any reason, resulting in a decrease in alveolar air content and a densification of the lung texture. The lung volume does not generally change (does not shrink) and may be slightly enlarged. Etiology: 1. Due to injury factors: (1) pneumonia: according to the pathogen can be divided into bacterial pneumonia, viral pneumonia, mycoplasma pneumonia, fungal infection of the lung, chlamydial pneumonia, etc., as the most common cause of solid lung changes. (2) pulmonary parasitic diseases: such as pulmonary schistosomiasis, schistosomiasis and Pneumocystis carinii, etc.; (3) physical and chemical factors such as radiation pneumonia and oxygen toxicity, etc. 2, abnormal immune response: such as metaplastic pulmonary infiltrates (allergic pneumonia, pulmonary hemorrhage-nephritis syndrome, etc.). 3, pulmonary circulatory dysfunction: such as cardiogenic pulmonary edema, pulmonary embolism, etc. 4, other such as acute respiratory distress syndrome, alveolar protein deposition, etc.