Tissue death as a result of an inadequate blood supply or infection of a wound
- Smoking, a high-fat diet, lack of exercise, and excess weight are risk factors
- Age, gender, and genetics as risk factors depend on the cause
Gangrene involves death of the tissues in a particular area of the body, most commonly the legs and feet, and is a potentially life-threatening condition.
There are two types of gangrene: dry and wet. Dry gangrene occurs when the tissues become deprived of oxygen as a result of a reduced blood supply. Tissue death is localized and does not spread from the affected site. Wet gangrene is less common and occurs when tissue that has been damaged by a wound or by dry gangrene becomes infected with bacteria. Infection is often due to clostridia, which are bacteria that thrive in dead tissues where there is no oxygen and produce a foul-smelling gas. The infection may spread to surrounding healthy tissues and can be fatal.
The reduction in blood supply that leads to gangrene is most often due to a blood clot forming in an artery (see Thrombosis and embolism), which may already be narrowed by the accumulation of fatty deposits on vessel walls, known as atherosclerosis. The tissues in the legs and feet are most commonly affected by these underlying conditions (see Lower limb ischaemia). The risk of an artery becoming blocked is increased by certain lifestyle factors, such as smoking and a high-fat diet. People with diabetes mellitus are more likely to develop gangrene as a result of progressive damage to the small blood vessels (see Diabetic vascular disease). Frostbite may also lead to the development of gangrene.
What are the symptoms?
The symptoms of dry gangrene may develop gradually or may appear over a few hours, depending on how quickly the blood supply is reduced. If the legs are affected, symptoms include:
Pain in the leg and foot.
Pale, cold skin, which becomes red and hot before turning purple and eventually black over several days.
If the gangrene is due to an infection, additional symptoms may be present, including pus around the affected area and fever. Infection may spread to the bloodstream (see Septicaemia).
What might be done?
Your doctor will probably be able to diagnose gangrene from its appearance. He or she may arrange for you to have pulse volume recording or Doppler ultrasound scanning to measure blood flow in the limb. You may require contrast X-rays, sometimes combined with MRI, to look for a blocked artery.
If you have gangrene, you will be admitted to hospital without delay. Intravenous antibiotics will be given to prevent or treat infection and, if possible, the blood supply to the gangrenous tissue will be restored. If an artery is obstructed, the vessel may be widened using angioplasty, in which a balloon on the tip of a catheter is passed into the narrowed area and then inflated. Alternatively, surgery may be carried out to remove or bypass the blockage (see Femoral artery bypass graft). The gangrenous tissue will be removed, and, if it has become infected, some of the living tissue around the gangrenous area will also be removed to prevent the infection from spreading. In some cases, amputation of a limb is necessary. If you develop wet gangrene, you may be placed in a chamber containing high-pressure oxygen to destroy the bacteria.
The earlier gangrene is diagnosed, the better the outlook, because blood supply to the affected tissues is more likely to be restored. A good blood supply promotes tissue healing after surgery. Gangrene is fatal in about 1 in 5 people, usually because of infection in the bloodstream.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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