The lesion range can be acinar, leaflet, lung segment or lung lobe. Lesions are distributed as bilateral asymmetrical  subpleural wedge-shaped or fan-shaped, mostly in the caudal lesions of the lung and dorsal subpleural area. When interlobular septa and intralobular interstitium are thickened, this is displayed as subpleural reticulation according to a “crazy paving” pattern. The underlying pathological changes are pulmonary edema, protein exudation, thickening of intralobular interstitial, and multi-nucleated giant cells and macrophage infiltration in the alveolar cavity.