It is a serious condition that can result in amputation of a limb or death. It needs urgent treatment to halt the spread of tissue death as rapidly as possible.
Diabetes also affects the small arterial vessels and they become insufficient to supply the extremity. Other risk factors are smoking and conditions such as Raynaud's disease.
Here are some key points about gangrene. More detail is in the body of this article.
- Gangrene occurs when a lack of blood supply, and therefore oxygen, results in tissue death.
- Gangrene is usually external, affecting the extremities, but it can also affect internal tissues.
- Surgical complications can lead to internal gangrene, with signs of toxic shock.
- Urgent treatment is important to prevent further serious illness and death. This includes removal of dead tissue and sometimes amputation.
What is gangrene?
Gangrene refers to the death and rotting of skin tissue and skin cells.
The two main forms of gangrene are known as dry and wet gangrene.
Other types, such as Fournier's gangrene and internal gangrene, are less common.
Dry gangrene is sometimes called mummification. It starts more slowly than wet gangrene, and it is most commonly associated with chronic disease, including diabetes.
The skin becomes dry, shriveled, and usually dark in color, ranging from brown to purplish-blue and feels cool or cold to touch.
In wet or moist gangrene, the skin swells and blisters form and may rupture. Pus may appear.
It is generally associated with infection of the dead tissue. Wet gangrene can develop following a severe burn or frostbite.
This type of gangrene can occur in people with diabetes who have an injury but do not notice or attend to it due to diabetic neuropathy.
Wet gangrene needs immediate treatment, as it can spread quickly and be fatal.
Gas gangrene, also called clostridial myonecrosis, is a particularly virulent form of wet gangrene.
Dry forms result from a progressive loss of blood supply to tissues. Dry forms can become wet forms if they develop a bacterial infection.
Deep or crushing injuries sustained in bacteria-rich conditions, such as a battlefield, can lead to gangrene.
All forms of gangrene happen because of a loss of blood supply to a certain area. This deprives tissue of oxygen and nutrients, causing the tissue to die.
Dry forms can also result from:
- Vascular problems: Most commonly due to the poor health of arteries and veins in the legs and toes. This usually develops over time due to conditions such as diabetes, peripheral arterial disease, and high blood pressure.
- Severe burns, scalds, and cold: Heat, chemical agents, and extreme cold, including frostbite, can all lead to dry gangrene. Wet gangrene may develop later.
- Raynaud's disease: There is impaired circulation to the ends of fingers and toes, especially in cold weather. Raynaud's is implicated in some cases of gangrene.
- Diabetes: Imbalanced blood sugar levels can damage blood vessels and nerves, reducing the oxygen supply to extremities.
Wet forms can develop from:
- Injury: Deep, crushing, or penetrating wounds that are sustained in conditions that allow bacterial infection can lead to gangrene. Examples are war zones and railway, machinery, and street accidents, if lacerated and bruised tissues are contaminated.
- Dry gangrene: If the area is infected with bacteria.
- Embolism: The sudden blockage of an artery can lead to dry gangrene, but it also increases the risk of infection, and therefore wet gangrene.
- Immune deficiency: If an immune system is weakened, for example by HIV, diabetes, long-time alcohol or drug abuse, or recent chemotherapy or radiotherapy, minor infections escalate more quickly and can become gangrenous.
Risk factors for gangrene include:
- obesity, diabetes, high blood pressure, and other causes of vascular disease
- excessive alcohol intake, which can lead to nerve damage
- impaired immune function, due for example, to HIV infection, chemotherapy, and radiation therapy
- intravenous drug use
Rarely, gangrene is linked to use of the anticoagulant drug, warfarin.
The major features of wet or dry gangrene are:
- Loss of color in the affected body part: The area will become discolored and eventually turn dry and dark. The color will change from red to black in dry gangrene, or it will become swollen and foul-smelling in wet gangrene. Gas gangrene will produce particularly foul-smelling, brownish pus.
- Shiny appearance to the skin and the shedding of skin, with a clear line forming between affected and healthy skin.
- Pain that is later followed by loss of sensation and an inability to move the part.
The part will be cold to the touch, and there will be a loss of pulse in the arteries.
Gangrene of the internal organs is slightly different but also involves tissue death.
There may not be any external signs of internal gangrene, but the following may occur as a result of septic shock and other complications:
- fever and chills
- nausea, vomiting, and diarrhea
- low blood pressure leading to light-headedness and fainting
- shortness of breath and increased heart rate
Gas gangrene can produce all of these symptoms, and others. The infected area of skin can quickly extend, with some changes visible within minutes.
In gas gangrene, the skin may:
- be very painfully swollen
- be pale at first, but become red or bronze before finally turning blackish-green
- show blisters filled with brown-red fluid
- produce a foul-smelling brown-red or bloody fluid when the affected tissue is drained or leaks, known as a serosanguineous discharge
- create a crackling sensation, or crepitus, on examination, due to the movement of gas under the skin
This is known as subcutaneous emphysema. The gas is produced by the infectious bacteria and is highly toxic, causing the necrosis to spread quickly.
Gas gangrene is very serious and immediately life threatening.
A doctor will carry out a physical examination and take a medical history, to find out about symptoms and potential exposure to infection or trauma.
They will look for signs of shock.
If gangrene is suspected, further diagnostic tests will be used to determine the type and extent of the necrosis, and to detect or rule out gas gangrene.
Tests can include:
- an X-ray to reveal gas bubbles in muscle tissue
- MRI and CT scans to determine the extent of muscle involvement
Tests of blood, tissue, and any discharge may be carried out to identify any bacterial infection.
Surgery may be necessary to explore the extent of the necrosis and to gain tissue samples.
Surgical removal of dead tissue may also be part of the treatment.
Treatment depends on the type, location, and extent of diseased tissue.
Anyone with suspected symptoms of gangrene needs immediate medical attention, to reduce the risk of serious complication and death.
The most severe form, gas gangrene, is fatal without treatment.
Treatment may involve the following emergency measures:
- intravenous antibiotics
- surgical removal of dead tissue, including amputation of an extremity or a limb to halt the wider spread
Reconstructive surgery may be possible, including skin grafting and other techniques.
Hyperbaric oxygen therapy
Gangrene can be treated in a hyperbaric chamber using oxygen therapy.
Hyperbaric oxygen therapy (HBOT) has shown some promise in supporting surgery and antibiotics.
A hyperbaric chamber of high-pressure oxygen improves oxygen supply to the wounds by encouraging the formation of new blood vessels, and by causing greater dissolution of oxygen in the plasma.
Exactly how HBOT works is unclear.
Treatment takes place in a pressure chamber, and it involves inhaling pure oxygen at 2.5 times the normal air pressure for between 30 and 120 minutes.
20 or more sessions may be necessary.
Side effects can include pressure-related trauma to the ears or nose and temporary near-sightedness.
Supervision by a qualified professional can prevent decompression sickness and non-lethal convulsions caused by oxygen toxicity.
Measures to help people who are susceptible to gangrene reduce their risk include:
- looking daily for cuts, sores, redness, swelling, skin breaks, or discharge on the feet
- having a medical foot health check once a year
- avoiding home-use chemical preparations for corns, calluses, and in-growing toenails
- preventing infection by washing wounds with mild soap and warm water, being sure to clean between the toes, and keeping them clean and dry
- watching out for signs of frostbite if exposed to prolonged cold
- avoiding walking outside barefoot, or wearing shoes without socks
- making sure footwear fits well and does not rub
- seeking urgent medical attention if the skin becomes pale, hard, cold, and numb, or if any color changes occur
- checking for injuries if there are complications due to nerve damage in diabetes, especially in the feet
- controlling body weight to prevent diabetes, arterial disease, and poor wound healing
- quitting smoking
For those at risk, regular visits to a podiatrist for foot care and treatment can reduce the risk of gangrene developing.