The four stages of the pathology of lobar pneumonia are the congestive phase, the red hepatic phase, the gray hepatic phase, and the dissipative phase. The pathologic changes are characterized by congestion and edema of the lung tissue during the congestive phase and plasma exudation in the alveoli; the red hepatic phase is dominated by red cell infiltration; the gray hepatic area is dominated by leukocyte infiltration; and then leukocytes phagocytose the bacteria and enter the dissipative phase, where the fibrin exudate is dissolved and absorbed and the alveoli are re-inflated to restore normal lung tissue. Lobar pneumonia, seen on clinical imaging, is in the red hepatic and gray hepatic phases, in which the pathologic stages are not actually precisely demarcated, and with early application of antimicrobial therapy, this typical pathologic staging has become rare. The prognosis of lobar pneumonia is good, and the lung tissue structure is mostly undamaged after the lesions dissipate, leaving no fibrous scarring. Only very few patients have incomplete absorption of fibrin in the alveoli, or even fibroblast formation, leaving mechanized pneumonia.