Gangrene can develop when the supply of blood to one or more areas of your body becomes blocked.
This blockage can occur in one of three ways:
- when an underlying health condition such as diabetes causes damage to a section of blood vessels
- infection – which in most cases is a bacterial infection
- injury
The role of blood
Blood contains two important components that the body’s cells require for life:
- oxygen
- nutrients, such as glucose, amino acids and fatty acids
Without an uninterrupted supply of oxygen and nutrients, the body’s cells lose the ability to function, and they die.
Blood contains:
- white blood cells, which eat bacteria and then die forming pus
- T-cells (‘T’ stands for thymus, an organ in the body which helps produce T-cells), whose job is to produce antibodies and help fight bacteria and viruses
Therefore, if the blood supply to a certain part of your body is cut, not only will tissue die but dead tissue will have a far higher risk of spreading any infection.
Gangrene and long-term conditions
Any long-term (chronic) condition that can affect your blood vessels and arteries has the potential to cause gangrene, particularly if the condition is poorly managed. These include:
- type 1 and type 2 diabetes – high levels of blood sugar associated with these conditions can damage blood vessels
- atherosclerosis – where arteries narrow and become clogged with a fatty substance known as plaque (risk factors for atherosclerosis include smoking and having high cholesterol levels)
- peripheral arterial disease – in which a build-up of fatty deposits in the arteries restricts blood supply to leg muscles (people with diabetes, atherosclerosis and/or high cholesterol levels often go on to develop peripheral arterial disease)
Blood vessels are already narrow, so any damage or extra narrowing can block blood flow to a part of the body.
Diabetic foot ulcers
Gangrene often develops as a complication of an open wound or sore that develops on the skin of the feet (a diabetic foot ulcer).
If you have diabetes, you may be more at risk of developing foot ulcers as a result of:
- reduced sensation
- reduced blood supply
These are described in more detail below.
Reduced sensation
High blood sugar associated with diabetes can damage nerves (peripheral neuropathy), particularly in your feet. Once damaged, the nerves are unable to transmit sensations of pain to your brain. Therefore it is easy to damage or injure yourself without realising.
As a result, you may continue walking without protecting the wound. This can make the wound worse and it may develop into an ulcer.
Reduced blood supply
High blood sugar can damage your blood vessels, restricting blood supply to your feet. Less blood means your feet will also receive a lower number of infection-fighting cells, and wounds will take longer to heal.
Reduced sensation means you are more likely to develop an ulcer, and reduced blood supply means the ulcer is more likely to become infected. The infection is likely to restrict the blood supply further, leading to gangrene.
If you have type 1, or type 2, diabetes, it is essential you take extra care of your feet. You should get your feet checked regularly by a podiatrist (a medical professional, also known as a chiropodist, who specialises in foot care). Read more about the prevention of gangrene.
Gangrene and injury
Wet gangrene often develops as a result of a traumatic injury, such as a car accident or burn. The injury causes a sudden loss of blood to an area of your body, causing the tissue in that area to become infected with bacteria.
Frostbite can also lead to wet gangrene.
Gangrene and surgery
It is estimated that just under half of all wet gangrene cases occur as a result of infection that develops during surgery. However, due to advances in surgical techniques and infection control, the chances of gangrene developing during surgery are very rare.
Gangrene and infection
Gangrene that results from infection, such as gas gangrene, or necrotising fasciitis, is very rare.
However, if your immune system is seriously weakened, minor infections may turn into serious infections. This can lead to gangrene developing.
Factors known to weaken the immune system and increase the risk of developing infection associated with gangrene include:
- chemotherapy
- radiotherapy
- HIV
- diabetes (both type 1 and type 2)
- chronic alcohol misuse
- injecting drugs, such as heroin
- malnutrition – where a person’s diet does not contain sufficient nutrients to meet the demands of their body
- being over 60 (the older you are, the less efficient your immune system is)
- obesity – being overweight with a body mass index (BMI) of 30 or above
- kidney failure
- dead tissue caused by a severe injury
However, for reasons still uncertain, a significant number of cases of necrotising fasciitis occur in young and otherwise healthy people.
