Gangrene
Definition
- Gangrene is a necrotic area invaded by saprophytic organisms leading to putrefaction.
Types of gangrene
- There are three types of gangrene
- Dry gangrene
- Moist gangrene
- Gas gangrene
Dry gangrene
Dry gangrene represents an area of coagulation necrosis resulting from infarction followed by mummification. The extremities of the body like tail, ears, legs and udder are affected.
- Causes
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Toxins (phytotoxins and ergotoxins): The toxins cause marked peripheral arteriolar vasoconstriction and damage to capillaries leading to thrombosis and infarction.
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Fescue poisoning
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Cold (Frost bite): Direct freezing and ice crystal formation leading to cellular damage, vascular damage and ischaemic necrosis.
- Gross pathology
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Affected part is dry (dehydration due to exposure to environment), shrivel (dehydration) and brown to black (due to formation of iron sulphide: iron from haemoglobin degradation, sulphide from putrefaction), proliferation of bacteria due to unfavourable environment, temperature and moisture.
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However, at the junction of living and dead tissue, there is a line of demarcation due to active inflammatory reaction.
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Dry gangrene
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Moist gangrene
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Moist gangrene - Intussusception
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Histopathology
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Initial coagulation necrosis with a few bacterial multiplications. Later liquified due to rapid proliferation of bacteria and infiltrating neutrophils.
Gas gangrene
Anaerobic bacterial proliferation producing toxin and damaging the tissues. Examples: Clostridium perfringens, Clostridium septicum introduced by penetrating wounds. The clostridia proliferate in necrotic tissue under anaerobic environment and produce toxins which cause tissue damage. The Clostridia chauvoei spreads haematogenously from the intestine and lodges in muscle which requires some injury and necrosis for the spores to germinate and bacteria to proliferate.
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Gross pathology
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Histopathology
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Coagulative necrosis of muscle, bacteria, serosanguineous exudates and gas bubbles are seen
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Last modified: Sunday, 11 December 2011, 7:58 AM