gangrene

DISEASEHEALTH

GANGRENE | MORPHOLOGY AND ITS TYPES

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).

TYPES:-

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.

types of gangrene

DRY GANGRENE

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
  • trauma
  • 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.

dry gangrene

MORPHOLOGIC FEATURES:

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.

WET GANGRENE

It occurs in naturally moist tissues and organs such as:

  • mouth,
  • bowel,
  • lung,
  • cervix,
  • 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.

wet gangrene

MORPHOLOGIC FEATURES:

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.

GAS GANGRENE

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.

gas gangrene
FeatureDry GangreneWet Gangrene
SiteCommonly limbsMore common in bowel
MechanismsArterial occlusionMore commonly venous obstruction, thus less often arterial occlusion
MacroscopyOrgan dry, shrunken and blackPart moist, soft, swollen, rotten and dark
PutrefactionLimited due to very little blood supplyMarked due to stuffing of organ with blood
Line of demarcationPresent at the junction between healthy and gangrenous partNo clear line of demarcation
BacteriaBacteria fail to surviveNumerous present
PrognosisGenerally better due to little septicaemiaGenerally poor due to profound toxaemia

STRANGE MIND

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