Gangrene - what is gangrene?

Gangrene is a type of tissue death which occurs due to loss of blood supply. This may affect any part of the body but usually affects the peripheral extremities like feet, toes, fingers, hands, penis etc.

Gangrene causes

Gangrene may follow an injury or an infection or may also be a long-term condition that has caused stagnation of blood and slowed down blood circulation.

Diabetes is the commonest cause of gangrene. According to estimates from Diabetes UK, those with diabetes are fifteen times more likely to require a major amputation of a limb commonly due to gangrene compared to the general population. In the UK around 5,000 people with diabetes have an amputation as a result of gangrene annually. (1-4)

Gangrene symptoms

The common symptoms of gangrene include change of color of the affected area. The area first becomes red and then gets discoloured to brown and may finally become black.

There is additional loss of sensation over the area affected and this persists over the surrounding healthy skin as well. There may also be excruciating pain in some types of gangrene.

The tissues that are affected show up with black blisters and there is a foul-smelling pus beneath the thinned skin at the area.

Gangrene types

Gangrene is of two major types - Dry and wet gangrene.

Dry gangrene

Dry gangrene occurs when there is slowing or obstruction in blood flow to parts of the body like toes and fingers.

Type 1 and type 2 diabetes mellitus leads to dry gangrene due to the high blood sugar and the damage the diabetes causes to the blood vessels that take blood to the fingers and toes.

Arteriosclerosis leads to thickened walls of the arteries or formation of cholesterol plaques and narrowing of the diameter of the small vessels leading to gangrene.

Similarly, peripheral artery disease leads to fatty deposits in the arteries and stops blood from flowing to the fingers and toes leading to gangrene.

Dry gangrene is usually limited to the part affected and there is an area of healthy skin just beyond the affected area. The area involved turns cold, dry and black and eventually falls off. This is called mummification of the area.

Wet gangrene

Wet gangrene is seen after serious injury or frost bite or even a burnt area becomes infected and the infection takes root deep into the tissues.

The infection leads to swelling of the tissues and this blocks the blood supply to the affected area making the infection worse and the gangrene progressive.

Wet gangrene can spread much quicker leading to life-threatening complications like septic shock if not treated immediately.

Gas gangrene

Gangrene may also be caused by special bacteria called Clostridium. This is called gas gangrene. This was a common infection seen during wars.

Necrotising fasciitis is caused when bacteria spreads into the skin and invades deeper tissues.

Internal gangrene

Gangrene may also affect internal organs when blood flow to them is obstructed. This is called internal gangrene and may affect the gall bladder or the intestines trapped within a hernia.

Fournier’s gangrene

When gangrene affects the penis and the genitalia it is called Fournier’s gangrene.

Treatment of gangrene

Gangrene needs to be treated immediately on detection. The sooner the condition is treated the better the outcome and this usually means avoidance of possible amputation of the limb or fingers/toes affected with the condition to prevent spread.

Surgery is the usually first line of treatment. This type of surgery is called debridement.

Along with surgery antibiotics against the organism affecting the area are used. These may usually be administered as injections for more rapid action and may be followed up with oral antibiotic pills once the gangrene shows signs of healing.

Gangrene especially in diabetes may be prevented by adequate foot care and good blood sugar control. A healthy diet, regular exercise and stoppage of smoking may go a long way in prevention of gangrene.

Types of gangrene

Gangrene essentially means death of tissues due to lack of blood supply and invasion of deeper tissues with infection.

Gangrene may be broadly classified into two types – dry and wet gangrene.

There are several other types of gangrene that are rarer. However, all types of gangrene manifest either as dry or wet form.

Dry gangrene

In this type of gangrene there is obstruction or slowing of blood flow into the organ or part of the body that is affected. Peripheral parts like toes, fingers, tip of the nose, earlobes etc. are commonly involved.

Dry gangrene is usually seen in patients of type 1 and type 2 diabetes. In both types of diabetes long term high blood sugar damages the small arteries and blood vessels that supply the end parts of the body like fingers and toes. This leads to obstruction and slowing of blood flow and ultimately gangrene.

In patients with high cholesterol, or dyslipidemia, there is a risk of deposition of cholesterol and lipids called plaques within the blood vessels. In the peripheries like toes and fingers this leads to decrease in the blood vessel diameters by narrowing of the lumen. This may lead to formation of gangrene.

Patients with peripheral arterial disease develop fatty acid deposits or develop narrowing of peripheral blood vessels. Some conditions include Raynaud’s disease and Scleroderma. This restricts blood supply to hand or leg muscles and may cause gangrene.

Dry gangrene is usually characterized by cold, painless and dry and shrivelled up affected part. There is surrounding healthy skin. The area affected is said to appear mummified.

Wet gangrene

Wet gangrene occurs when infection and bacteria invade deeper tissues after injuries, frost bites, foot ulcers or burns. There is excessive swelling of the affected part due to release of the toxins from the invading bacteria.

This leads to blockage of the blood supply and worsening of the infection as the fighter cells of the body (white blood cells) cannot reach the area affected via blood vessels.

Wet gangrene can spread much quicker than dry gangrene and may lead to life-threatening complications like septic shock if not treated immediately.

Wet gangrene appears discoloured or black usually with acute and excruciating pain. There are black blisters and foul-smelling pus beneath the thinned skin at the area.

As infection is associated with release of discharge and pus, it is known as “wet”.

Other types of gangrene

Other types of gangrene include:

Gas gangrene

This is caused by bacteria called Clostridium. This is found in spores present in the soil. Gas gangrene was a common cause of death in the wars.

The gangrene is caused by the toxins released by the bacteria. This may be of three further types:

    • traumatic gas gangrene occurring after injury
    • non-traumatic gas gangrene
    • recurrent gas gangrene caused by C. perfringens species of bacteria.

Necrotising fasciitis

Necrotising fasciitis (NF) is a deep tissue infection caused by bacteria like Staphylococcus or Streptococcus. The bacteria spreads into the skin and into the tissues. This bacteria attacks the soft tissue and the fascia, which is a sheath of tissue covering the muscle. NF can occur in an extremity following a minor trauma, or after some other type of opportunity for the bacteria to enter the body such as surgery. The Group A Strep infection (flesh eating bacteria) is most common with minor trauma. A mixed bacterial infection is often the cause after surgery.

Internal gangrene

This is cause when blood supply to an internal organ is hampered usually by pressure from another organ or growth. For example, in hernia there is an abnormal opening where the intestine may get blocked and the blocked area turns gangrenous.

Noma or cancrum oris

This is a type of gangrene affecting the face.

Fournier’s gangrene

Fournier's gangrene (FG) is a rare but life threatening disease that affects the penis and the genitalia. FG has been shown to have a predilection for patients with diabetes as well as long term alcohol misuse; however, it can also affect patients with non‐obvious immune compromise.  The development and progression of the gangrene is often fulminating and can rapidly cause multiple organ failure and death. Because of potential complications, it is important to diagnose the disease process as early as possible Although antibiotics and aggressive debridement have been broadly accepted as the standard treatment, the death rate remains high.(5)

Meleney's synergistic gangrene

This is a rare type seen in patients after surgery. Meleney's synergistic gangrene is caused by S aureus and streptococcus organisms. One of the identifying symptoms is the presence of extremely painful lesions, which usually form in the second week after surgery or minor trauma. (6)

Causes of gangrene

Gangrene is caused due to tissue death that results from stoppage of blood supply to the affected organ.

Blood vessels carry red blood cells that in turn carry life giving oxygen to all tissues. Blood also carries nutrients, such as glucose, amino acids, and fatty acids essential for the normal functioning of the tissues. The white blood cells in addition are fighters that fight against the invading bacteria.

Obstruction in blood flow thus results in deprivation of all these components necessary for normal functioning. As the blood supply is blocked the cells lose the ability to function and die. (1-5)

Blockage of blood supply

This blockage of blood supply may occur in three different ways –

  • Damage to the blood vessels due to an underlying condition like diabetes, arteriosclerosis or peripheral artery disease.

While diabetes damages the smaller blood vessels, due to high blood sugar and resultant chemical reactions at the molecular level, both arteriosclerosis and peripheral artery disease lead to narrowing of the arteries.

  • Infections leading to swelling of the affected organ and stoppage of blood flow. This is commonly seen in wet gangrene.
  • Injury to the blood vessels coupled with infections. This is seen in traumatic gas gangrene.

Diabetes and gangrene

Diabetes further raises the risk of gangrene since gangrene develops as a complication of an open wound or sore.

Diabetics in addition have damaged small nerves of the hands and especially feet and toes called peripheral neuropathy. This makes them less sensitive to small injuries that may leave open sores prone to infections. Due to high blood sugar these infections refuse to heal and may lead to gangrene.

Causes of wet gangrene

Wet gangrene often develops as a result of a traumatic injury like an automobile accident, gunshot wound, burns or wound due to a sharp instrument.

The injury causes a sudden loss of blood to the affected area due to damage to blood vessels. This leads to infection and invasion by bacteria. Infections may also develop after a surgery. This is rare.

Gangrene and people with weak immune systems

People with a weak immune system are also prone to infections that may lead to gangrene. These people include:

  • those with HIV AIDS
  • those with cancer and on chemotherapy and radiotherapy
  • smokers
  • long term alcoholics
  • long term drug abusers
  • diabetics
  • those with severe malnutrition or deficient diets
  • elderly
  • obese
  • the overweight
  • those with long term end stage kidney disease

Causes of gas gangrene

Gas gangrene was a common occurrence until the middle of the 20th century when war injuries were exposed to spores containing the causative bacteria present in soil. During the Civil War in the USA nearly half of the soldiers receiving gunshot wounds developed infection with many progressing to gas gangrene.

The primary organism causing gas gangrene is Clostridium perfringens. The spores of the bacteria are carried in animal feces and are present in the soil.

Other organisms that lead to gangrene in these conditions include Group A Streptococci and Staphylococci, C. histolyticum or other Clostridium spp. Gas gangrene has become uncommon in modern warfare due to better surgical management and treatment.

Traumatic gas gangrene is caused after a deep, penetrating injury like a knife or a gunshot wound or a car crash. This type of trauma accounts for about 70% of cases of gas gangrene and Clostridium perfringens is found in about 80% of such infections. Other organisms are:

  • C. septicum,
  • C. novyi,
  • C. histolyticum,
  • C. bifermentans,
  • C. tertium
  • C. fallax.

Necrotizing fasciitis (Type II) is also called streprtococcal gas gangrene and is caused due to group A streptococci. This is seen in those who have sustained an injury with a blunt instrument, after child birth, long term intravenous drug abuse or penetrating injury such as caused by a laceration or a surgical procedure.

Fournier’s gangrene

Fournier’s gangrene is caused in the genitalia. It is caused by the Bacteroides spp. and peptostreptococci.

The spread of the infection is via gastrointestinal tract or via urinary tract. This type of gangrene is seen in diabetics.