Gangrene
Gangrene is necrosis and subsequent decay of body tissues caused by infection or thrombosis or lack of blood flow. It is usually the result of critically insufficient blood supply sometimes caused by injury and subsequent contamination with bacteria. This condition is most common in the extremities.
Dry gangrene
Dry Gangrene begin the distal part of the limb due to ischaemia. the typical example of the dry gangrene is the toes and feet of an old patient due to arteriosclerosis. the gangrene spreads slowly upwards until it reaches the point where the blood supply is adequate to keep the tissue viable.Macroscopically, the effecetd part is dry, shrunken and dark black, resembling the foot of a mummy. it is black due to liberation of hemoglobin from hemolysed red blood cell which is acted upon by the hydrogendisulfide(HG) produced by the bacteris resulting in formation of black iron sulfide. the line of seperation usually brings about complete seperation with eventual falling off of the gangrenous tissue if it is not removed surgically.
If the blood flow is interrupted for a reason other than severe bacterial infection, the result is a dry gangrene. Persons with impaired peripheral blood flow, such as diabetics, are at greater risk for dry gangrene.
The early signs of dry gangrene are a dull ache and sensation of coldness in the area, along with pallor of the flesh. If caught early, the process can sometimes be reversed by vascular surgery. However, if necrosis sets in, the affected tissue must be removed just as with wet gangrene.
Internal gangrene
In this gangrene the tissues become white. It is located inside the body, usually after surgery or trauma. Also called "white gangrene".
Wet gangrene
Wet Gangrene Occurs in naturally mosit tissue and organs such as the mouth, bowel, lung, cervix vulva, etc. Diabetic foot is another example of wet gangrene due to high sugar content in the necrosed tissue which favour the growth of bacteria. Bedsores occuring in a bed-ridden patient due to preassure site like like sacrum, buttocks and heels are the other important clinical condition included in wet gangrenw. In wet gangrene, the tissue is effected by saprogenic microorganisms (Bac.perfringes, fusiformis, putrificans, etc), becomes swollen and emits fetid smell. It develops in the tissue rich in water: Lungs, Intestine, noma(water cancer) gangrene of cheeks in children at measles. Wet gangrene usually develops rapidly due to blockage of venous and/or arterial blood flow. The affected part is stuffed with blood which favour the rapid growth of bacteria. the toxic products formed by bacteria are absorbed causing systemic manifestation of septicemia and finally death. Macroscopially the effected part is swollen edematpus, soft, putrid, rotten, dark. the part is dark due to the same mechanism as in dry gangrene.
Gas gangrene
Main article: Gas gangrene
Gas gangrene is a bacterial infection that produces gas within tissues in gangrene. It is a deadly form of gangrene usually caused by Clostridium perfringens bacteria. Due to its tendency to progress rapidly, it is considered a medical emergency. The rapid progression of gas gangrene occurs because of the tendency of expanding gas to open and separate the internal tissues, progressively exposing more and more healthy tissue to infection.
Gas gangrene is caused by exotoxin-producing clostridial species, which is mostly found in soil, and other anaerobes (e.g. Bacteroides and anaerobic streptococci). These environmental bacteria may enter the muscle through a wound and go on to proliferate in necrotic tissue and secrete powerful toxins. These toxins destroy nearby tissue, generating gas at the same time. A gas composition of 5.9% hydrogen, 3.4% carbon dioxide, 74.5% nitrogen and 16.1% oxygen was reported in one clinical case