Classes of Gangrene

Types/ Classes of gangrene:

There are three major types of gangrene-

1.      Moist gangrene,

2.      Dry gangrene and

3.      Gas gangrene.

1.      Moist gangrene:

Moist gangrene occurs in the tissues which have more blood supply but less drainage during development of necrosis. It occurs in visceral organs (lungs, intestine, uterus, mammary gland, vulva). It is the most common type of gangrene. It follows both arterial and venous obstructions in the area.

Gross characteristics:

1.      The gangrenous part is swollen, moist, softened, pulpy and darker.

2.       Cool and insensitive to touch with foul smelling.

Microscopic characteristics:

1.      Mixture of coagulation and liquefaction necrosis along with large number of saprophytic bacteria.

2.      Presence of spherical gas bubbles less in number in the area.

3.      Complete obliteration of histological structures of gangrenous part.

Dry Gangrene

Dry gangrene occurs in the tissues which have less blood supply but more drainage during development of necrosis.

It occurs in-

•      Skin,

•      Tail,

•      Ear,

•      Extremities.

It follows arterial obstruction in the area.

Gross characteristics:

1.      The gangrenous part is shrivelled, dry and red to brown to dark in colour.

2.       Cool and insensitive to touch with foul smelling.

Microscopic characteristics:

1.      Coagulation necrosis along with less number of saprophytic bacteria.

2.      Presence of zone of inflammation between gangrenous and normal tissue.

3.      Complete obliteration of histological structures of gangrenous part.

Gas Gangrene

Gas gangrene occurs in the tissues when gas forming bacteria invade the necrotic tissue.

It is deadly form of gangrene.

It occurs in-

•      Any tissue or organ in the body.

Cause:

A group of bacteria of clostridial species causes gas gangrene.

•      Black leg/ black quarter (Clostridium chauvoei),

•      Malignant edema (C. septicum),

•      Necrotic enteritis (C. perfringens),

•      Black disease (C novyi).

These bacteria are spore-forming and anaerobic. After invading, they release exotoxins which produce gas and causes toxemia and shock.

Gross characteristics:

1.      Oozing of brownish red discharge,

2.      Gas is produced in tissue and gives crepitation on palpation.

3.      Cool and insensitive to touch with foul smelling.

Microscopic characteristics:

1.      It depends on the tissue involved.

2.      In Black quarter, muscle fibers are necrotic and swollen with edema fluid and neutrophils.

3.      Complete obliteration of histological structures of gangrenous part may occur.