Gangrene can develop when the supply of blood to one or more areas of your body is interrupted.

This can occur as the result of an injury, an infection, or an underlying condition that affects your circulation.

Types of gangrene

There are several different types of gangrene, each with a different cause. The main types are:

• dry gangrene – where the blood flow to an area of the body becomes blocked
• wet gangrene – caused by a combination of an injury and bacterial infection
• gas gangrene – where an infection develops deep inside the body and the bacteria responsible begin releasing gas
• necrotising fasciitis – caused by a serious bacterial infection that spreads quickly through the deeper layers of skin and tissue
• internal gangrene – where the blood flow to an internal organ, usually the intestines, gallbladder or appendix, becomes blocked

Who's most at risk?

People most at risk of gangrene are those with an underlying health condition that can affect the blood vessels and arteries (particularly if it's poorly managed), and those with a weakened immune system.

Conditions affecting the blood vessels

Conditions that can affect the blood vessels and increase your risk of developing gangrene include:

• diabetes – a lifelong condition that causes a person's blood sugar level to become too high, which can damage nerves and blood vessels 
• atherosclerosis – where arteries narrow and become clogged with a fatty substance known as plaque
• peripheral arterial disease – where a build-up of fatty deposits in the arteries restricts blood supply to leg muscles
• Raynaud's – where blood vessels in certain parts of the body, usually the fingers or toes, react abnormally to cold temperatures

As blood vessels are naturally narrow, any damage or extra narrowing has the potential to block blood flow to a part of the body and cause gangrene.

Diabetes

People with diabetes have an increased risk of developing gangrene. This is because the high blood sugar levels associated with the condition can damage your nerves, particularly those in your feet, which can make it easy to injure yourself without realising.

High blood sugar can also damage your blood vessels, restricting the blood supply to your feet. Less blood means your feet will also receive fewer infection-fighting cells, so wounds will take longer to heal and are more likely to become infected.

It's therefore important that you take extra care of your feet if you have diabetes. Read more about foot care in preventing gangrene.

Injuries and surgery

You're also at an increased risk of developing gangrene if you experience a traumatic injury or serious damage to your skin and tissues, such as:

• a serious injury – for example, during a car accident
• a burn
• frostbite

These injuries can cause a sudden loss of blood to an area of your body, and any open wounds can become infected with bacteria.

Gangrene can also occur as a result of an infection that develops during surgery. However, with advances in surgical techniques and infection control, the chances of gangrene developing during surgery are small nowadays.

Weak immune system

If your immune system is seriously weakened, minor infections can become more serious and can lead to gangrene. A weak immune system can be caused by:

• chemotherapy or radiotherapy
• HIV
• diabetes
• long-term alcohol misuse
• injecting drugs, such as heroin
• malnutrition
• being over 60 years of age (the older you are, the less efficient your immune system is)
• obesity
• kidney failure

However, for reasons that are unclear, gangrene can sometimes occur in young and otherwise healthy people.

A diagnosis of gangrene is based on a combination of physical examination, medical history and tests.

Your doctor will want to find out whether you have any long-term health conditions, or if you've recently experienced any injuries that could have caused the condition.

They'll also examine the affected area to check for any obvious signs of gangrene, such as a foul odour or discolouration of the skin.

A number of tests and investigations can be carried out to confirm the diagnosis of gangrene. These include:

• blood tests to check for an infection.
• fluid or tissue culture – where a small tissue or fluid sample from the affected area is tested to find out which bacteria are responsible for the condition and determine the most effective antibiotic to treat it with
• blood cultures – where a sample of blood is taken and put into special culture bottles and placed in a warm environment (incubated) to encourage the growth of bacteria so they can be examined further
• imaging tests – a range of imaging tests, such as X-rays, magnetic resonance imaging (MRI) scans or computerised tomography (CT) scans can be used to confirm the presence and spread of gangrene; these tests can also be used to study blood vessels so any blockages can be identified
• surgery – a surgical examination under anaesthetic may be necessary to confirm a diagnosis of gangrene deeper inside the body

As gangrene is a potentially serious condition, treatment is usually started before the results of any tests become available.

Treatment for gangrene involves removing the affected tissue, preventing infection or treating any existing infection, and treating the problem that led to gangrene developing.

For example, if gangrene is caused by a poor blood supply, surgery may be used to repair damaged blood vessels. If gangrene is caused by an infection, strong antibiotics may be used as well as surgery.

Removing dead tissue

Surgery to cut out the dead tissue, known as debridement, is often necessary to prevent the gangrene from spreading and to allow the surrounding healthy tissue to heal.

Larval debridement therapy (biosurgery)

In some cases, it may be possible to use larval debridement therapy, also known as biosurgery, instead of conventional surgery to remove the dead tissue.

Certain types of fly larvae are ideal for this because they feed on dead and infected tissue but leave healthy tissue alone. They also help fight infection by releasing substances that kill bacteria and stimulate the healing process.

Maggots used for larval therapy are specially bred in a laboratory using eggs that have been treated to remove bacteria. The maggots are placed on the wound and covered with gauze, under a firm dressing, which keeps them on the wound (and out of sight). After a few days, the dressing is cut away and the maggots are removed.

Amputation

In severe cases of gangrene, where a whole body part, such as a finger, toe, or limb, is affected and debridement is unlikely to help, amputation may be considered.

Amputation can prevent gangrene spreading to other parts of the body and can be used to remove a severely damaged limb so an artificial (prosthetic) limb can be fitted.

Unless immediate emergency treatment is needed, a decision to amputate will only be made after a full discussion between you and the health professionals treating you.

Treating infection

Gangrene that's caused by an infection can usually be treated with antibiotics, which can be given as tablets or injections.

Injections are usually necessary if you need surgery or you have a severe infection. Injecting antibiotics directly into a vein allows larger doses to be given and means that they're more likely to reach the affected area.

To counter the effects of infection and accelerate the healing process, you'll also need fluids and nutrients into a vein (intravenous fluids) and you may need blood transfusions.

Restoring blood flow

In some cases, surgery may be carried out to restore the blood flow to the affected area. The main techniques used to achieve this are:

• bypass surgery – where the surgeon redirects the flow of blood and bypasses the blockage by connecting (grafting) one of your veins to a healthy part of an artery
• angioplasty – where a tiny balloon is placed into a narrow or blocked artery and is inflated to open up the vessel; a small metal tube, known as a stent, may also be inserted into the artery to help keep it open

Research suggests that both techniques are equally effective in restoring blood flow and preventing the need for amputation in the short-term. An angioplasty has the advantage of having a faster recovery time than bypass surgery, although it may not be as effective in the long-term as bypass surgery.

Hyperbaric oxygen therapy

Hyperbaric oxygen therapy is an alternative treatment for some types of gangrene.

During hyperbaric oxygen therapy, you sit or lie down in a specially designed chamber filled with pressurised air. A plastic hood that provides pure oxygen for you to inhale is placed over your head.

This treatment results in high levels of oxygen being dispersed into your bloodstream and reaching the affected areas (even those with a poor blood supply), which speeds up healing.

For gangrene caused by a bacterial infection, the oxygen can also stop some types of bacteria (particularly the type responsible for gas gangrene) producing the toxins that allow the infection to spread, preventing further tissue damage.

Hyperbaric oxygen therapy has proved effective in treating gangrene caused by infected diabetic foot ulcers, reducing the risk of amputation.

However, evidence relating to the effectiveness of hyperbaric oxygen therapy in treating other types of gangrene is limited and further research is required. Hyperbaric oxygen therapy also isn't currently widely available in the UK.

Reconstructive surgery

Reconstructive surgery using a skin graft may be used to cover the area of skin damaged by gangrene.

During a skin graft, the surgeon will remove healthy skin from another part of your body (usually a part that would be covered by clothing), and reconnect it over the damaged area

There are a number of things you can do to help lower your risk of developing gangrene.

Foot care

If you have diabetes or another long-term condition that can cause atherosclerosis (hardening or thickening of the arteries), it's important you take extra care of your feet.

If you have diabetes, you should have your feet checked at least once a year. However, you may need more frequent check-ups if you have additional risk factors, such as peripheral neuropathy (numbness in the hands and feet), or a history of foot ulcers.

The advice listed below can help prevent a diabetic foot ulcer developing:

• Check your feet daily for problems such as numbness, discolouration, breaks in the skin, pain or swelling. Report problems to your GP immediately.
• Don't use chemical preparations for corns and calluses or ingrown toenails. Instead, contact a podiatrist (a healthcare professional who specialises in foot care).
• Wash your feet daily with warm water. Afterwards, make sure you dry your feet thoroughly, particularly between the toes.
• Wear shoes that fit properly and don't squeeze or rub. Ill-fitting shoes can cause corns and callouses, ulcers and nail problems.

If you have a history of foot ulcers, wearing specially designed therapeutic or orthopaedic shoes can help prevent further ulcers developing. Your podiatrist may be able to provide you with specially made-to-measure footwear, or they may be able to recommend a stockist.

Find out more about taking care of your feet with type 1 diabetes and type 2 diabetes.

Smoking

Smoking can cause your arteries to become blocked, resulting in a loss of blood supply to your arms or legs. This is known as peripheral arterial disease (PAD).

If you do decide to stop smoking a good first step is to contact Help Me Quit which will provide dedicated help and advice about the best ways to give up.

If you're committed to giving up smoking but don't want to be referred to a stop smoking service, your GP should be able to prescribe medical treatment to help with any withdrawal symptoms you may experience.

For more information about giving up smoking, see stop smoking.

Diet

Eating an unhealthy diet high in fat will make any existing atherosclerosis worse and increase your risk of developing gangrene.

Continuing to eat high-fat foods will cause more fatty plaques to build-up in your arteries. This is because fatty foods contain cholesterol.

There are 2 types of fat – saturated and unsaturated. Avoid foods that contain saturated fats because they increase levels of "bad cholesterol" in your blood.

Foods high in saturated fat include:

• meat pies
• sausages and fatty cuts of meat
• butter
• ghee (a type of butter often used in Indian cooking)
• lard
• cream
• hard cheese
• cakes and biscuits
• food containing coconut or palm oil

Read more about healthy eating.

Alcohol

Drinking excessive amounts of alcohol will cause your blood pressure to rise, and also raise the level of cholesterol in your blood.

Men and women are advised not to drink more than 14 units a week. 14 units is equivalent to 6 pints of average-strength beer or 10 small glasses of low-strength wine.

Read more about alcohol units and get tips on cutting down.

Exercise

A healthy, well-balanced diet and regular exercise will keep your blood pressure and cholesterol levels at a healthy level, helping prevent your blood vessels becoming damaged.

Unless advised otherwise by your doctor, you should be aiming for at least 150 minutes (2.5 hours) of moderately intense physical exercise a week.

Moderate intensity physical activity is any activity that increases your heart and breathing rate. It may make you sweat but you'll still be able to hold a normal conversation. Examples include:

• fast walking
• cycling on level ground or with few hills
• swimming
• tennis

You should choose physical activities you enjoy because you're more likely to continue doing them.

It's probably unrealistic to meet these exercise targets immediately if you haven't exercised much in the past. Aim to start gradually and build up the amount of exercise you do over time.

Read more about health and fitness.