Gangrene

How gangrene develops

Tissue needs a constant blood supply to deliver oxygen and remove waste. When blood flow stops or is severely reduced, cells die. When bacteria invade dying tissue, they release toxins that kill more tissue and can spread into the bloodstream. Dead tissue cannot recover, so treatment aims to save the living tissue around it.

Types of gangrene

See gas gangrene and Fournier gangrene for more on those forms.

Causes and risk factors

• Peripheral artery disease: narrowed leg arteries from atherosclerosis. Advanced disease, called critical limb ischemia, causes rest pain, ulcers and gangrene.
• Diabetes: damages blood vessels and nerves, so foot injuries go unnoticed and heal poorly. A diabetic foot ulcer can become infected and progress to gangrene.
• Smoking: a major cause of arterial disease.
• Frostbite: freezing damages tissue and blood vessels.
• Severe injury, burns and crush injuries.
• Infections: necrotizing soft tissue infections, including necrotizing fasciitis.
• Raynaud's phenomenon in severe cases, especially with scleroderma.
• Blood clots or emboli that suddenly block an artery.
• Septic shock and medicines that constrict blood vessels in intensive care.
• Weakened immunity, obesity, kidney disease, alcohol use disorder and injecting drug use.

Symptoms

Dry gangrene

• cold, numb skin
• color changing from red to brown, purple, blue and finally black
• shriveled, dry tissue that may eventually separate on its own
• pain before the tissue dies, then numbness

Wet and gas gangrene

• swelling and severe pain
• blisters or sores with foul-smelling discharge
• skin that turns red, bronze, purple or black
• crackling under the skin (gas)
• fever, fast heart rate, low blood pressure, confusion: signs of sepsis

Internal gangrene

• severe, persistent pain in the belly or chest
• fever, vomiting and signs of shock

Diagnosis

• examination of skin color, temperature, pulses and sensation
• blood tests for infection, kidney function and sepsis
• tissue or fluid cultures to identify bacteria
• imaging: X-ray or CT to look for gas in tissues, and MRI for deep infection
• vascular studies: ankle-brachial index, Doppler ultrasound, CT or conventional angiography to map arterial blockages
• surgical exploration when necrotizing infection is suspected

Treatment

Removing dead tissue

• Debridement: surgical removal of dead tissue, sometimes repeated.
• Amputation: of a toe, foot or part of a limb when the tissue cannot be saved or infection is life-threatening.
• Maggot (larval) therapy is occasionally used to clean wounds.

Treating infection

• IV antibiotics, chosen according to cultures. Gas gangrene and necrotizing infections need urgent combined antibiotics and surgery.
• Hyperbaric oxygen therapy may help in gas gangrene and some diabetic wounds.

Restoring blood flow

• angioplasty and stenting, or bypass surgery for arterial blockages
• clot-dissolving treatment or clot removal for sudden blockages

Supportive care

• treatment of sepsis in intensive care
• wound care, pain control, nutrition
• blood sugar control
• rehabilitation and prosthetics after amputation

Prevention

• stop smoking
• control blood sugar, blood pressure and cholesterol
• with diabetes: check your feet daily, wear well-fitting shoes, never walk barefoot, and see a podiatrist regularly
• treat any foot wound promptly
• dress warmly and protect fingers and toes from frostbite
• seek early care for wounds that become red, swollen or painful

Frequently asked questions

What are the first signs of gangrene?

Early signs include skin that becomes pale, red or blue, cold and numb, with pain or tingling. As tissue dies, it turns purple or black. In wet gangrene, the area swells, blisters and produces foul-smelling discharge. Fever and feeling unwell suggest infection spreading.

What is the difference between dry and wet gangrene?

Dry gangrene develops slowly from poor blood flow and leaves dry, shriveled, black tissue without infection. Wet gangrene involves bacterial infection, with swelling, blisters, discharge and a bad smell, and can spread quickly and cause sepsis. Dry gangrene can become wet if infected.

Can gangrene be cured?

Dead tissue cannot be revived, but gangrene can be treated by removing dead tissue, treating infection and restoring blood flow. Early treatment can save much of the limb. Advanced cases may need amputation to stop spread and save life.

How fast does gangrene spread?

Dry gangrene usually progresses slowly over weeks to months. Wet gangrene can spread within hours to days. Gas gangrene and Fournier's gangrene can spread within hours and are life-threatening, so emergency care is needed for rapidly spreading color change, swelling and fever.

Who is at risk of gangrene?

People with diabetes, peripheral artery disease, a history of smoking, frostbite, severe injuries, weakened immune systems or obesity are at higher risk. People with diabetes and reduced foot sensation are especially vulnerable because small injuries can go unnoticed.