Gangrene can develop when the supply of blood to an area of your body is interrupted.

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

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

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 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.