Gangrene Pathology

Study Notes

Definition: Massive tissue necrosis followed by putrefaction
Causes: Necrosis caused by sudden ischemia or bacterial toxins, putrefaction caused by saprophytic bacteria breaking down protein of necrotic tissue

Occurs in limbs with arterial occlusion (e.g. thrombus, embolus, surgical ligature)
Pathological features:
- Massive necrosis occurs distal to site of occlusion
- Dryness of necrotic tissue due to drainage and evaporation of fluids
- Saprophytic bacteria invade necrotic tissue causing putrefaction and bad odour
- Tissue attains black stain due to hydrogen sulfide units with iron of hemoglobin
- Gangrenous process advances slowly along the limb as inflammation causes thrombosis within the vessels
- Toxins of putrefaction irritate adjacent tissue, causing zone of acute inflammation in neighboring healthy part (line of demarcation)
- Granulation tissue grows towards gangrenous part with formation of groove (line of separation)

Line of demarcation: Narrow zone of inflammation between healthy and gangrenous tissue
Line of separation: Groove between healthy and necrotic zone, level of tissue separation
Line of demarcation is above line of separation

Causes: Sudden arterial and venous occlusion
Occurs mainly in internal organs where no evaporation of fluids can occur
Rapid spread of toxins and rapid putrefaction due to presence of fluids
Line of demarcation is poor, line of separation is absent, and toxemia is marked
Seen in crushed limb injuries and diabetic patients due to hyperglycemia and poor body resistance

Definition: Subtype of moist gangrene where bacteria cause both necrosis and putrefaction
Example: Cancrum oris caused by treponema Vicenti and bacillus fusiformis

Definition: Moist gangrene mainly of muscles, occurring in deep wounds contaminated by manured soil containing anaerobic spores
Caused by saccharolytic bacteria (e.g. Cl. Welchi) or proteolytic bacteria (e.g. Cl. sporogens)
Tissue destruction causes ischemia that facilitates germination of spores
Gangrenous tissue stains red or black depending on the type of bacteria

Definition: State of tissue hypoperfusion due to inadequate effective circulating blood volume
Clinical picture:
- Confused patient
- Pale and cold skin
- Rapid weak pulse, low blood pressure, and shallow rapid breathing