Gangrene – Necrosis with superadded putrefaction

Gangrene is a form of necrosis of tissue with superadded putrefaction.This is a type of coagulative necrosis that occurs due to ischaemia(e.g. in bowel, limb etc.).
Gangrene is classified into 3 types –
1. Dry gangrene
2. Wet gangrene
3. Gas gangrene

Dry Gangrene is a form of gangrene that occurs in the distal part of the limb due to ischaemia. One of the typical examples of a dry gangrene is on the toes and feet of an old patient due to Atherosclerosis.
Some other causes of Gangrene foot are Thromboangiitis obliterans(Buerger’s disease), Raynaud’s disease, trauma, Ergot’s poisoning.
Dry gangrene is usually initiated at the toe region which is farthest from the blood region, and contains very less blood where invading bacteria to grow into the necrosed tissue. This gangrene slowly grows slowly upwards and reaches a point where the blood supply is adequate enough to keep the whole tissue viable.
A “Line of separation” is formed between the gangrenous part and the viable part.

Wet gangrene is a type of gangrene that usually occurs in the moist tissues and organs such as the Mouth, Bowel, Lung, Cervix, Vulva etc. Diabetic leg is another example with high sugar content in the necrosed tissue which is favorable for the bacteria to grow.
Bedsores occurring in bedridden patients due to pressure on sites like the sacrum, buttocks and the heels is one more consideration of wet gangrene. Wet gangrene usually develops rapidly due to blockage of venous and less commonly arterial blood flow from thrombosis or embolism.
At the affected part, stuffed blood encourages the formation and growth of the invading bacteria. And the toxic products formed by the bacteria are absorbed causing the systemic manifestations of septicaemia, and then finally to death. There is no clear demarcation of any line of separation.

Gas gangrene is a special form of wet gangrene that is caused by a gas-forming Clostridia(which is a gram positive anaerobic bacteria), which enters into the tissues through open contaminated wounds, normally in the muscles. Or this invasion can also occur as a compilation of operation on colon which usually contains the bacteria Clostridia. The bacteria produces many toxins which can produce necrosis and oedema locally and are absorbed producing systemic manifestations.