In lobar pneumonia, the presence of fibrinosuppurative exudate with disintegration of red cells is seen in the stage of -
Ref:Textbook of pathology (Harsh mohan) 6th edition,page no.468 STAGE OF CONGESTION: INITIAL PHASE . The initial phase represents the early acute inflammatory response to bacterial infection and lasts for 1 to 2 days. Grossly, the affected lobe is enlarged, heavy, dark red and congested. Cut surface exudes blood-stained frothy fluid. Histologically, typical features of acute inflammatory response to the organisms are seen. These are as under i) Dilatation and congestion of the capillaries in the alveolar walls. ii) Pale eosinophilic oedema fluid in the air spaces. iii) A few red cells and neutrophils in the intra-alveolar fluid. iv) Numerous bacteria demonstrated in the alveolar fluid by Gram's staining. 2. RED HEPATISATION: EARLY CONSOLIDATION This phase lasts for 2 to 4 days. The term hepatisation in pneumonia refers to liver-like consistency of the affected lobe on cut section. Grossly, the affected lobe is red, firm and consolidated. The cut surface of the involved lobe is airless, red-pink, dry, granular and has liver-like consistency. The stage of red hepatisation is accompanied by serofibrinous pleurisy. Histologically, the following features are observed. i) The oedema fluid of the preceding stage is replaced by strands of fibrin. ii) There is marked cellular exudate of neutrophils and extravasation of red cells. iii) Many neutrophils show ingested bacteria. iv) The alveolar septa are less prominent than in the first stage due to cellular exudation. 3. GREY HEPATISATION: LATE CONSOLIDATION This phase lasts for 4 to 8 days. Grossly, the affected lobe is firm and heavy. The cut surface is dry, granular and grey in appearance with liverlike consistency.. The change in colour from red to grey begins at the hilum and spreads towards the periphery. Fibrinous pleurisy is prominent. Histologically, the following changes are present i) The fibrin strands are dense and more numerous. ii) The cellular exudate of neutrophils is reduced due to disintegration of many inflammatory cells as evidenced by their pyknotic nuclei. The red cells are also fewer. The macrophages begin to appear in the exudate. iii) The cellular exudate is often separated from the septal walls by a thin clear space. iv) The organisms are less numerous and appear as degenerated forms. 4. RESOLUTION . This stage begins by 8th to 9th day if no chemotherapy is administered and is completed in 1 to 3 weeks. However, antibiotic therapy induces resolution on about 3rd day. Resolution proceeds in a progressive manner. Grossly, the previously solid fibrinous constituent is liquefied by enzymatic action, eventually restoring the normal aeration in the affected lobe. The process of softening begins centrally and spreads to the periphery. The cut surface is grey-red or diy brown and frothy, yellow, creamy fluid can be expressed on pressing. The pleural reaction may also show resolution but may undergo organisation leading to fibrous obliteration of pleural cavity. Histologically, the following features are noted: i) Macrophages are the predominant cells in the alveolar spaces, while neutrophils diminish in number. Many of the macrophages contain engulfed neutrophils and debris. ii) Granular and fragmented strands of fibrin in the alveolar spaces are seen due to progressive enzymatic digestion. iii) Alveolar capillaries are engorged. iv) There is progressive removal of fluid content as well as cellular exudate from the air spaces, paly by expectoration but mainly by lymphatics, resulting in restoration of normal lung parenchyma with aeration.
Congestion
Red hepatization
Gray hepatization
Resolution
Respiratory system