Science Fair Project Encyclopedia
Gangrene is necrosis (death) and subsequent decay of body tissues caused by many number of things including infection, thrombosis and lack of blood flow. It is most commonly the result of critically insufficient blood supply sometimes caused by an injury and subsequent contamination of the wound with bacteria. This condition is most common in the extremities. The best of all possible treatments is revascularization (restoration) of the affected organ, which can reverse some of the effects of necrosis and allow healing. Depending on the extent of tissue loss and location treatment other than revasularization runs the gamut from allowing digits to auto-amputate (fall off), debridement and local care, to amputation, the removal of infected, necrotic tissues.
Gangrene caused by a serious bacterial infection is called wet gangrene. Gangrene caused by lack of circulation in an injured or diseased area is called dry gangrene.
One specific example of gangrene is so called diabetic foot that can be seen in long-standing complicated diabetes. It is caused by a combination of arterial ischemia, injury and poor healing that is rather common in diabetics. It often combines poor healing with a superimposed infection. The picture here is of a foot with a recent amputation of a great toe and yet increasing loss of circulation (the bluish area) with subsequent tissue loss to come.
The most common surgical treatment for irreversible gangrene is amputation.
In the years before antibiotics, fly maggots were commonly used to treat chronic wounds or ulcers to prevent or stop necrotic spread. Maggots only consume dead flesh. Their use largely died out after the introduction of antibiotics and enzyme treatments for wounds. In recent years, however, maggot treatment has regained some credibility and is sometimes employed to great effect in cases of chronic tissue necrosis.
Wet gangrene is perhaps the more familiar of the two types, at least in media portrayals. An injury, such as a gunshot or laceration, leads to a bacterial infection, which produces pus. If the pus does not drain well, the blood supply to the area is blocked, and with it, the oxygen. With its oxygen supply cut off, the tissue dies.
Treatment of the underlying infection is necessary, as is removal of the dead tissue. Without treatment, the infection can spread further and destroy increasing amounts of tissue. Eventually, sepsis and death can result.
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.
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