Gangrene is a serious and often life-threatening condition where the body’s tissue begins to decay and die as a result of an interruption in the blood supply.
Gangrene can occur as a result of:
- injury
- infection
- a chronic (long-term) condition that affects blood circulation
Conditions where gangrene is a potential complication include:
Smoking also increases your risk of developing gangrene.
Types of gangrene
There are several different types of gangrene:
Dry gangrene
Dry gangrene usually affects the body’s extremities, such as the hands or feet. It occurs when one or more of your arteries become blocked. The lack of blood supply causes the affected tissue to slowly die, but there is no infection.
The area of your body that is affected by dry gangrene usually looks darker and feels cold. Over several weeks the body part will dry out and wither, before eventually dropping off.
Dry gangrene is common in people who have chronic (long-term) conditions that affect their blood supply, such as arteriosclerosis.
Wet gangrene
Wet gangrene often occurs through a combination of injury and infection. An injury such as a burn, frostbite or a crush injury (where the body is subjected to a high degree of force or pressure, usually after being squeezed between two heavy objects) can suddenly restrict the flow of blood to tissue.
Blood contains antibodies that fight infection, so without a regular blood supply, tissue can quickly become infected by bacteria.
The swelling that is caused by the infection can further restrict the blood supply, which means that wet gangrene can spread quickly around the body. The condition is potentially life-threatening and needs immediate emergency medical treatment. Wet gangrene often occurs in people who have diabetes, following an injury to their foot or toe.
Necrotising fasciitis
Necrotising fasciitis is a form of gangrene that spreads quickly and is caused by a serious bacterial infection. Necrotising fasciitis is sometimes referred to as flesh-eating bacteria.
It occurs when bacteria enter a cut in the skin and quickly spread, releasing harmful toxins (poisons). These block the supply of blood to surrounding skin tissue, causing it to die.
Necrotising fasciitis usually affects people who have seriously weakened immune systems (immunocompromised). However, for reasons that are unclear, cases have also been reported in previously fit and healthy people.
Gas gangrene
Gas gangrene is similar to necrotising fasciitis, but the infection develops deeper inside the body, such as inside the muscles, usually as the result of a trauma or a surgical wound.
The bacteria responsible for gas gangrene (clostridium) thrives in environments where there is little or no oxygen (anaerobic). It begins to produce gases, while also releasing dangerous toxins. Like necrotising fasciitis, gas gangrene can be life-threatening and requires emergency medical treatment.
Internal gangrene
Internal gangrene can develop when the blood flow to an internal organ, usually the intestine, gallbladder or appendix, is blocked. This often occurs as a complication of a hernia (when an internal part of the body, such as an organ, pushes through a weakness in the muscle or surrounding tissue wall). Internal gangrene is life-threatening and requires surgery.
How common is gangrene?
Every year, 5,000 people with diabetes have an amputation (where part of the body is cut off) as a result of gangrene.
People with diabetes are 15 times more likely to have an amputation as a result of gangrene compared with people who do not have diabetes.
There is limited data about other types of gangrene because as they tend to occur as complications of emergency medical conditions, they are not recorded in the same way. However, occurrences of other types of gangrene are thought to be rare. For example, each year in the UK, it is estimated that there are 500 cases of necrotising fasciitis.
Outlook
If dry gangrene is detected and treated early enough, the outcome is usually favourable.
The outlook for wet gangrene, gas gangrene, and necrotising fasciitis is less favourable. This is because they are caused by infection, and bacteria often spreads into the blood (sepsis) which, in turn, can lead to multiple organ failure and a massive drop in blood pressure (septic shock).
It is estimated that 20-25% of people with a gangrene-associated blood infection die of the condition.
The outlook for internal gangrene is highly variable, depending on how quickly the condition is diagnosed and treated.
Treatments for gangrene include antibiotics and surgically removing the affected tissue. In severe cases, an affected body part may need to be surgically removed.