Outcomes of acute inflammation and the chronic inflammatory response
THE CONTEXT
Acute inflammation typically ends in resolution, connective tissue replacement, or progression to chronic inflammation. The outcome depends partly on the injury, affected tissue, and host response.
Complete resolution
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Resolution means that inflammation ends after elimination of the offending agent and the tissue returns to normal.
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It is usual when injury is limited or short lived, tissue destruction is minimal, and damaged parenchymal cells can regenerate.
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Macrophages remove cellular debris and microbes, while edema fluid is resorbed mainly through lymphatics.
Healing by scarring or fibrosis
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Connective tissue replacement occurs after substantial tissue destruction or injury to tissues incapable of regeneration.
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It also occurs when abundant fibrin exudates in tissues or serous cavities, such as the pleura or peritoneum, cannot be completely cleared.
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Connective tissue grows into the damaged area or exudate and converts it into a mass of fibrous tissue.
Progression to chronic inflammation
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Acute inflammation may become chronic when the injurious agent persists or the normal healing process is disrupted.
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Chronic inflammation lasts weeks to months and combines inflammation, tissue injury, and attempts at repair in varying proportions.
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It may follow acute inflammation or begin insidiously without a preceding acute reaction.
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Considerable tissue damage and scarring may occur despite relatively little inflammatory infiltrate, as illustrated by hepatic cirrhosis.