Gangrene is the death of skin and soft tissues resulting from a reduction in the supply of oxygen-carrying blood to the affected region - often the extremities.
A significant number of soldiers in the two world wars acquired the most serious, infectious form of gangrene, with more than half of those infected dying because of it.
It is a a serious condition that can be fatal; gangrene should be treated urgently to halt the spread of tissue death as soon as possible.
In this article, we will cover the different forms of gangrene, their symptoms, how they are diagnosed, and the available treatments.
Contents of this article:
Fast facts on gangrene
Here are some key points about gangrene. More detail and supporting information is in the body of this article.
- Gangrene is usually external, affecting the extremities, but it can also affect internal tissues.
- Gangrene is most commonly associated with chronic illness, such as a severe complication of diabetes, or acute causes, such as certain types of injury
- Wet gangrene can result from chronic disease if the dry gangrene becomes infected
- Surgical complication can lead to internal gangrene, which presents with signs of toxic shock
- Urgent treatment is important to prevent further serious illness and death and includes removal of dead tissue or perhaps amputation
What is gangrene?
More than half of soldiers affected by gangrene in the World Wars did not survive.
Dry gangrene is sometimes called mummification, this is the slow-onset form most commonly associated with chronic disease, including diabetes.
The skin is dry and shriveled, and the color is usually dark, ranging from brown to purplish-blue. Dry gangrene is commonly caused by blood vessel diseases such as atherosclerosis.
Wet gangrene is also known as moist gangrene. The skin swells and blisters and appears "wet." There may be pus.
It is generally associated with infection of the dead tissue. Wet gangrene can develop following a severe burn or frostbite.
Sometimes, this type of gangrene occurs in people with diabetes who have an injury (often on the foot), but because their sensitivity is reduced (due to diabetic neuropathy), they do not notice it and treat it. Wet gangrene should be treated immediately as it can spread quickly and be fatal.
Gas gangrene (also called clostridial myonecrosis) is a particularly virulent form of wet gangrene. This condition is associated with poorly cleansed wounds of the kind found in war. Sometimes, it can result from surgery.
Dry forms, which are the result of a progressive loss of blood supply to tissues, can become wet forms if they also develop a bacterial infection.
Causes of gangrene
All forms of gangrene result from the loss of blood supply to a certain area - often at the extremities - which deprives tissue of oxygen and nutrients, causing the tissue to die (necrosis).
Further causes of gangrene include:
Complications of diabetes affecting the extremities are a risk factor for gangrene.
- Vascular - dry gangrene is most commonly due to poor vasculature (arteries and veins) in the legs and toes. This usually develops over time due to conditions like diabetes and high blood pressure.
- Surgery - an operation can sometimes shut off blood supply in such a way as to cause gangrene. This form is usually dry but can also become wet gangrene.
- Mechanical constriction - for example, gangrene can be revealed when pressure splints are removed. Trauma/injury can also cause mechanical constriction.
- Severe burns, scalds, and cold - heat, chemical agents, and cold (including frostbite) can all lead to dry gangrene; wet gangrene can develop.
- Raynaud's disease - this condition is characterized by impaired circulation to the ends of fingers and toes, especially in cold weather; Raynaud's is implicated in some cases of gangrene.
- Injury - deep, crushing, or penetrating wounds that are sustained in conditions that allow bacterial infection to take hold can lead to gangrene. Such conditions are often seen in war zones, as well as in railway, machinery, and street accidents if lacerated and bruised tissues are contaminated with dirt.
- Mechanical constriction - rarely, blood flow restriction caused by pressure from bandages, bone fractures, tumors, and so on, can lead to gangrene.
- Embolic gangrene - the sudden occlusion of an artery due to an embolism can lead to dry gangrene, but this can also increase the risk of infection and thus lead to wet gangrene
- Any case of dry gangrene can progress to wet gangrene if there is an opportunity for bacterial infection
Risk factors for gangrene include:
- Obesity, diabetes, and high blood pressure - causes of vascular disease
- Excessive alcohol intake, which can lead to nerve damage
- Impaired immune function - as a result of, for example, HIV infection, chemotherapy, and radiation therapy
- Intravenous drug use
- Rarely, the anticoagulant drug warfarin
Signs and symptoms of gangrene
The major features of gangrene are:
- Loss of color in the affected body part - initially discolored but eventually turning dry and dark, going through red to black color in dry gangrene, or being swollen and foul-smelling in wet gangrene (and, in gas gangrene, producing particularly foul-smelling, brownish pus)
- Shiny appearance to the skin; shedding of skin, 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
- Loss of pulse in 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
In addition to the features seen in more common types of gangrene, there are certain signs and symptoms peculiar to gas gangrene, a less common form of wet gangrene. In gas gangrene, the infected area of skin can quickly extend, with some changes visible in just a matter of minutes.
In cases of gas gangrene, the skin may:
- Be very painfully swollen.
- Be pale at first, but become red or bronze before finally turning blackish green.
- When palpated, create a crackling sensation (crepitus) due to the movement of gas under the skin (subcutaneous emphysema). The gas is produced by the bacteria causing infection and is highly toxic, causing the necrosis to spread quickly.
- Show blisters filled with brown-red fluid.
- Produce a foul-smelling brown-red or bloody fluid when the affected tissue is drained or leaks (a serosanguineous discharge).
Gas gangrene is very serious and quickly life threatening.
Diagnosis and tests for gangrene
Initial suspicion of gangrene calls for physical examination by a doctor, who will also take medical history, asking questions about symptoms and potential exposure to infection or trauma.
During the examination, the doctor will look for external signs and symptoms, as well as 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. These tests can include:
- X-ray - to reveal gas bubbles in muscle tissue
- MRI and CT - to determine the extent of muscle involvement
Tests may be ordered to identify any bacterial infection - confirmed by white blood cell counts, Gram staining, and sample culture - these can include:
- Blood tests
- Laboratory examination of samples of the tissue affected and any discharge
Surgery may be necessary to explore the extent of the necrosis and to gain tissue samples. Surgical removal of dead tissue may be part of the treatment of gangrene.
Treatment of gangrene
To reduce the risk of serious complication and death, gangrene requires emergency treatment. As such, it is important that anyone with suspected symptoms of gangrene seeks immediate medical attention.
In all cases of dry gangrene caused by chronic disease, prevention is far better than cure.
When gangrene is diagnosed, the particular treatment is dependent on the specific type, location, and extent of diseased tissue, but may involve the following emergency measures:
- Antibiotics administered directly into the bloodstream (intravenously)
- Removal of the dead tissue surgically, including amputation of an extremity or even a whole limb to halt the wider spread of gangrene
- Reconstructive surgery, involving skin grafting and other techniques, may be possible
Hyperbaric oxygen therapy
Hyperbaric oxygen therapy has shown some promise as a useful additional intervention to surgery and antibiotics; it may be helpful as part of the treatment plan.
The idea behind this treatment is that 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. However, the precise mechanisms behind hyperbaric oxygen therapy's effects remain unknown.
- Involves inhaling pure oxygen at the pressure of 2-3 absolute atmospheres (or 2-3 times 14.7 pounds per square inch)
- Takes place in a single- or multi-patient pressure chamber
- Usually lasts 90 minutes, but ranges between 70 and 120 minutes
- Is typically administered over 20 or more sessions
Frostbite can lead to gangrene if untreated.
People with risk factors for gangrene can take measures to protect themselves:
- Watch out for complications due to nerve damage in diabetes, especially in the feet - look for cuts, sores, redness, swelling, or discharge on the feet and hands every day, and have a medical check of foot health once a year
- Control body weight - to prevent diabetes, arterial disease, and poor wound healing
- Stop smoking
- Prevent infection - by washing wounds with a mild soap and water and keeping them clean and dry
- Look out for signs of frostbite if exposed to prolonged cold - seek urgent medical attention if the skin becomes pale, hard, cold, and numb, or if you notice any color changes