GANGRENE | MORPHOLOGY AND ITS TYPES
April 27, 2020
Gangrene is generally a type of necrosis of tissue with putrefaction add in it.
The type of necrosis is mainly coagulative because of ischemia. e.g. in gangrene of the bowel & limb.
On the other hand, gangrenous or necrotising inflammation defines by primary inflammation. provoked by bacteria resulting in massive tissue necrosis. Therefore, the result of necrotising inflammation & gangrene is the same. but the way two are produce is different.
The examples of necrotising inflammation are as following:
- gangrenous appendicitis
- gangrenous stomatitis ( i.e. noma, cancrum oris).
There are 2 main forms i.e.:-dry and wet. There is also a variant form of wet called gas gangrene. In all types, necrosis basically undergoes liquefaction by the action of putrefactive bacteria.
This form begins in the distal part of a limb due to ischaemia.
The typical example is in the toes and feet of an old patient due to arteriosclerosis.
Other causes include following:
- thromboangiitis obliterans ( e.g. Buerger’s disease)
- Raynaud’s disease
- ergot poisoning.
It generally initiated in one of the toes which is far away from the blood supply. So that even the invading bacteria find it hard to grow in the necrosed tissue.
The gangrene spreads slowly upwards. until it reaches a point where the blood supply is adequate to keep the tissue alive. A line of separation formed at this point between the gangrenous part & the alive part of the tissue.
Grossly, the affected part is basically dry, reduced, and dark black. It seems likewise the foot of a mummy.
Histologically, thus there is necrosis with smudging of the tissue. The line of separation consists of inflammatory granulation tissue is also found.
It occurs in naturally moist tissues and organs such as:
- vulva etc.
Diabetic foot is other example for wet gangrene. due to high sugar content in the necrosed tissue it favours growth of bacteria.
It generally lacks clear-cut line of demarcation. and can spread to peritoneal cavity causing peritonitis.
Grossly, the affected part is basically soft, swollen, decomposed, rotten, and dark.
Histologically, there is generally coagulative necrosis. Thus that has a stuffing of blood with the affected part.
It is generally a special form of wet gangrene. And this is basically caused by gas-forming clostridia (gram-positive anaerobic bacteria). This bacteria gain entry into the tissues through open contaminated wounds. especially in the muscles, or as a complication of operation on the colon which contains clostridia.
|Feature||Dry Gangrene||Wet Gangrene|
|Site||Commonly limbs||More common in bowel|
|Mechanisms||Arterial occlusion||More commonly venous obstruction, thus less often arterial occlusion|
|Macroscopy||Organ dry, shrunken and black||Part moist, soft, swollen, rotten and dark|
|Putrefaction||Limited due to very little blood supply||Marked due to stuffing of organ with blood|
|Line of demarcation||Present at the junction between healthy and gangrenous part||No clear line of demarcation|
|Bacteria||Bacteria fail to survive||Numerous present|
|Prognosis||Generally better due to little septicaemia||Generally poor due to profound toxaemia|