Page 66 - Textbook of Pathology, 6th Edition

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SECTION I

Figure 3.32 Dry gangrene of the foot. The gangrenous area is dry, shrunken and dark and is separated from the viable tissue by clear line of
separation.

Histologically, there is necrosis with smudging of the venous, and less commonly, arterial blood flow from
tissue. The line of separation consists of inflammatory thrombosis or embolism. The affected part is stuffed with
granulation tissue (Fig. 3.33). blood which favours the rapid growth of putrefactive
bacteria. The toxic products formed by bacteria are absorbed
Wet Gangrene causing profound systemic manifestations of septicaemia,
and finally death. The spreading wet gangrene generally
Wet gangrene occurs in naturally moist tissues and organs lacks clear-cut line of demarcation and may spread to
such as the mouth, bowel, lung, cervix, vulva etc. Diabetic peritoneal cavity causing peritonitis.
foot is another example of wet gangrene due to high sugar
General Pathology and Basic Techniques
content in the necrosed tissue which favours growth of MORPHOLOGIC FEATURES. Grossly, the affected part
bacteria. Bed sores occurring in a bed-ridden patient due to is soft, swollen, putrid, rotten and dark. The classic
pressure on sites like the sacrum, buttocks and heels are the example is gangrene of bowel, commonly due to
other important clinical conditions included in wet gangrene. strangulated hernia, volvulus or intussusception. The part
Wet gangrene usually develops rapidly due to blockage of is stained dark due to the same mechanism as in dry
gangrene (Fig. 3.34).
Histologically, there is coagulative necrosis with stuffing
of affected part with blood. There is ulceration of the
mucosa and intense inflammatory infiltration. Lumen of
the bowel contains mucus and blood. The line of
demarcation between gangrenous segment and viable
bowel is generally not clear-cut (Fig. 3.35).

Contrasting features of two main forms of gangrene are
summarised in Table 3.5.

GAS GANGRENE. It is a special form of wet gangrene
caused by gas-forming clostridia (gram-positive anaerobic
bacteria) which gain entry into the tissues through open
contaminated wounds, especially in the muscles, or as a
complication of operation on colon which normally contains
clostridia. Clostridia produce various toxins which produce
necrosis and oedema locally and are also absorbed producing
profound systemic manifestations.
MORPHOLOGIC FEATURES. Grossly, the affected area
is swollen, oedematous, painful and crepitant due to
Figure 3.33 Dry gangrene of the foot. Microscopy shows coagulative accumulation of gas bubbles within the tissues.
necrosis of the skin, muscle and other soft tissue, and thrombsed vessels.