Gangrene (Gr. gangraina, 'a gnawing'), or MORTIFICATION, is the death of a part of the body, whether external or internal. It is most common in the extremities, especially the feet. Its immediate cause is always arrest or impairment of the supply of blood to the affected part. This may be produced in various ways: (1) by direct mechanical injury, or by extreme heat (burn) or cold (Frost-bite, q.v.); (2) by severe septic inflammation, usually following injury, or attacking a wound; (3) by disease of the blood-vessels of the part, in combination perhaps with weak heart action. The second group includes the most dangerous and fatal forms of gangrene: Cancrum Oris (q.v.), phagedæna, and hospital gangrene, now happily much less common than they once were. The third includes gangrene occurring as a result of poisoning by ergot of rye, of diabetes, old age, &c.
The symptoms and appearances attending gangrene vary greatly in different cases. Its onset may be sudden or gradual; it may at once become limited, or it may have a constant tendency to extend; it may be preceded and accompanied by great pain, or may only be observed in consequence of the local loss of feeling. But in all cases the loss of vitality is accompanied by loss of natural warmth, of sensibility and of motion in the affected part, and by a change in its appearance. It may either become moist and swollen, or dry and shrivelled; and its colour may be either dark purple or greenish, or at least at first pale and waxy. The constitutional symptoms are equally variable: if the part affected be small and not vital, and the gangrene limited, they may be slight and of little importance; otherwise there is generally great depression, with rapid feeble pulse, foul tongue, and other signs of alarming illness.
If the gangrene be limited, a separation takes place gradually between the living and dead parts, and, if the patient survive, the disorganised and lifeless texture is thrown off, and the part heals by Cicatrisation (q.v.) or the formation of a scar, indicating the loss of substance. With regard to treatment, the strength must, generally speaking, be maintained by a nourishing but not too stimulating diet, and the part carefully preserved from external injury and from changes of temperature.
In some forms of gangrene amputation may afford the best or even the only chance of saving the patient's life; in others its results are disastrous, as it is almost certain to lead to fatal extension of the disease. Much care is therefore needed in deciding the question whether surgical interference should be resorted to.