What is Gangrene? What causes Gangrene?
A century since the First World War, gangrene remains a problem, albeit less deadly. Many soldiers in that war, and in the Second World War, too, acquired the most serious, infectious form of the skin and soft tissue disease that is now relatively rare - and half would die because of it.1
The distinctive smell of that "gas gangrene" was the only means to diagnose the condition in the battlefield, and this technique was described as far back as in the first half of the last millennium, in medieval times.1
Use this page to learn about the modern-day factors that lead to different forms of gangrene, and how doctors today manage the conditions.
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 a serious, sometimes life-threatening condition in which the skin, muscle and other tissues die as a result of lost blood supply.
- It is usually external, at the extremities, but can also affect internal tissues.
- Causes are most commonly chronic illness, such as a severe complication of diabetes, or acute, from certain types of injury, for example.
- Dry gangrene is caused by chronic illness, while wet gangrene - including gas gangrene - is usually an acute form involving bacterial infection and caused by injury, for example.
- Wet gangrene can result from chronic disease if the dry gangrene becomes infected.
- Surgical complication can lead to internal gangrene, which presents signs of toxic shock.
- Initial diagnosis is made based on the history leading up to the presentation, and a physical examination, including of any external appearance and smell, followed up by laboratory and imaging tests, and sometimes exploratory surgery.
- Urgent treatment is important to prevent further serious illness and death, and includes removal of dead tissue or even amputation.
- Prevention of gangrene is an important part of living with certain chronic illnesses, including diabetes. Doctors working in hospitals, especially those involved in abdominal surgery, also take steps to prevent gangrene.
What is gangrene?
Gangrene is a disease of the skin and soft tissues - and sometimes internal tissues and organs - that results in tissue death (necrosis). It comes in two broad forms:2-5
Crushing or penetrating wounds sustained in dirty conditions can lead to gangrene. Half of all soldiers affected by gangrene in the World Wars did not survive.
- Dry gangrene - sometimes called mummification, this is the slow-onset form most commonly associated with chronic disease, including diabetes
- Wet gangrene - also known as moist gangrene, this is the sudden onset (acute) form.
Gas gangrene (also called clostridial myonecrosis) is a particularly virulent form of wet gangrene.2,3,6,7 This is the condition that is associated with poorly cleansed wounds of the kind suffered in war - deep crushing or penetrating wounds that become infected with bacteria, Clostridium in particular. In addition to injury, the condition 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.5
What causes gangrene?
All forms of gangrene result from the loss of blood supply to tissue - often at the extremities - which, depriving it of oxygen and nutrients, causes the tissue to die (necrosis).2,5
Gangrene is sometimes called mortification, and the process is distinguished by a portion - a slough - of tissue dying en masse, as opposed to ulceration, which involves death at a molecular or cellular level.5
The reasons underlying the process of ischemic death differ by the specific type of gangrene. Broadly:5
- In dry gangrene, the necrosis is caused by slow, progressive loss of blood supply
- Wet gangrene results from a sudden loss of perfusion, and is worsened by the involvement of bacteria.
Diabetes and blood vessel diseases such as atherosclerosis are the most common causes in dry gangrene.4
For older people with a common complication of undiagnosed or uncontrolled diabetes - diabetic foot - dry gangrene is more likely to set in. Here, blood circulation to the feet worsens, and there is a higher likelihood of any foot wounds going unnoticed by the patient. This is because of diabetic neuropathy, which is a loss of sensation resulting from nerve damage caused by the diabetes.
Complications of diabetes affecting the extremities, especially the feet, are a risk factor for gangrene, partly because painless wounds can go unnoticed.
Further causes of gangrene include:5
- "Senile gangrene" caused by "aged" blood vessels, and so usually affecting older people. But arteriosclerosis can also occur in younger people whose arteries have narrowed due to having, for example, a combination of syphilis and alcohol dependency.
- Surgery - an operation involving the ligation of an artery, as treatment of an aneurysm for example, can 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 (especially carbolic acid, but also caustic potash, and nitric or sulphuric acid), and cold (including frostbite) can all lead to dry gangrene. If treatment involves wet or oily dressings and there are septic conditions, wet gangrene can develop.
- Raynaud's disease - a condition in which spasm of blood vessels is thought to cause the reduced circulation to the ends of fingers and toes of people affected, especially in cold weather.
- Angiosclerosis and intermittent claudication can be associated with gangrene.
- Eating large quantities of coarse rye bread - the ergot consumed is implicated.
- Injury - especially when deep crushing or penetrating wounds are sustained in conditions that allow bacterial infection to take hold. War zones create these conditions, but so too can railway, machinery, and street accidents if lacerated and bruised tissues are contaminated with soil/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 be liable to infection and so lead to wet gangrene.
- Any case of dry gangrene can progress to wet gangrene if there is an opportunity for bacterial infection.
Dry forms
Wet forms
Overlap
Risk factors for gangrene, the first three of which are also culprits in blood vessel disease and diabetes, include:3,4
- Smoking
- OBESITY
- Excessive alcohol intake
- Impaired immune system (immunosuppression) - as a result of, for example, HIV infection, chemotherapy, and radiation therapy
- Intravenous drug use
- Rarely, the anticoagulant drug warfarin, especially if used in combination with heparin.
Signs and symptoms of gangrene
The telltale features of gangrene are:2-4,6,7
- Loss of color in the affected 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
- Coldness
- Pain that is later followed by loss of sensation and an inability to move the part
- Loss of pulse in arteries.
If the gangrene is internal, there may not be any external signs, but the following may occur, including because of the septic shock that can result:3,4
- Fever and chills
- Confusion
- Nausea, vomiting, and diarrhea
- Low blood pressure leading to lightheadedness and fainting
- Shortness of breath and high heart rate.
Signs and symptoms that are peculiar to gas gangrene, a less common form of wet gangrene, include the below in addition to the features above common to other types. The area of skin infected can extend quickly, so that changes can be visible over the course of even minutes. The skin may:2-4,7,8
- Be very painfully swollen
- Be pale initially, but become red or bronze before finally turning blackish green
- When palpated, can create a crackling sensation (crepitus) as gas under the skin (subcutaneous emphysema) is moved around (the gas is produced by the bacteria involved 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 tissue affected is drained or leaks (a serosanguineous discharge).
Certain muscles are more likely to be affected by gas gangrene - at the sides of the trunk, under the arms, or in the buttocks, thighs or calf muscles.8
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