Gangrene of the toes and foot: dry, wet and how surgery helps

What causes gangrene and where it starts

Gangrene in the foot comes from a lack of blood, infection or injury, and these often act together.⁠^[1,7]

• Ischemic gangrene is caused by a lack of blood flow and usually appears on the forefoot, including the toes.⁠^[2] Artery disease with gangrene, pain at rest or a wound open over 2 weeks is called chronic limb-threatening ischemia and needs urgent referral to a vascular specialist.⁠^[2] See peripheral artery disease.
• Infective gangrene can follow a skin infection (cellulitis) in a foot with nerve damage and reduced circulation: the infection inflames the blood vessels there (septic vasculitis), and the tissue dies.⁠^[9]

The risk is higher with diabetes, blood vessel disease, a serious injury, a weakened immune system, or after surgery.⁠^[7]

Dry, wet and gas gangrene

• Dry gangrene usually develops slowly as circulation fails, mostly in the toes. The tissue becomes numb, dry and wrinkled and may eventually separate on its own.⁠^[3,4]
• Wet gangrene is dead tissue complicated by infection. The area swells, reddens and drains pus.⁠^[3]
• Gas gangrene is a fast-moving, life-threatening infection caused by gas-forming bacteria, most often Clostridium.⁠^[3]

Dry gangrene doesn’t always stay dry: wet and gas gangrene often start as dry, stable gangrene.⁠^[10] In a review of 100 consecutive patients who had forefoot amputations for gangrene, about half needed urgent surgery for acute infection, and bone samples showed bone infection (osteomyelitis) in nearly 80%.⁠^[10]

Signs to watch for

• skin on a toe or part of the foot that turns blue or black
• foul-smelling drainage
• loss of feeling in the area, sometimes after a spell of severe pain
• swelling, redness and pus around a dark area, which point to wet gangrene, an emergency⁠^[7,3]

With nerve damage and poor circulation, signs of infection can be muted, so a darkening toe deserves attention even if it doesn’t hurt.⁠^[9,7] For other causes of a color change or swelling, see dark, black or blue toes and a red, hot, swollen foot.

How gangrene is evaluated

• Circulation. With diabetes and gangrene, guidelines recommend checking the foot pulses, Doppler waveforms and the ankle-brachial and toe-brachial indexes, since no single test rules out artery disease.⁠^[1] We do noninvasive circulation testing at our practice; arterial duplex or angiography is arranged with vascular specialists. See circulation tests for foot wounds.
• Infection. Tests can include X-rays, blood tests and cultures of tissue or fluid.⁠^[7] We take X-rays on site; MRI or CT is arranged at outside imaging centers. Bone removed at surgery can be tested for hidden infection.⁠^[10]
• Staging. In the WIfI system (Wound, Ischemia, foot Infection), any gangrene limited to the toes is wound grade 2, a level of tissue loss that can still be managed within the foot, with toe amputations up to a transmetatarsal amputation.⁠^[2] See how a foot wound is evaluated.

Dry gangrene: blood flow first, then a planned operation

With diabetes, artery disease and gangrene, a vascular specialist should be consulted urgently to time any blood-flow procedure and any drainage surgery; the aim is a straight path of blood to at least one artery of the foot.⁠^[1] Vascular specialists perform angioplasty, stents and bypass; we refer you and plan foot surgery around their work. See restoring blood flow.

Meanwhile we see you regularly to keep the area clean, dry and free of pressure, and to watch for signs that it is turning wet. Hyperbaric oxygen is no substitute for restoring blood flow: it is not advised for saving a limb while severe ischemia is uncorrected.⁠^[2] If a wound still won’t heal once blood flow is restored, we can discuss a referral for hyperbaric oxygen therapy.

Once blood flow is restored, most people with foot gangrene are evaluated for a minor amputation, with the wound closed in stages or after a short delay, or rebuilt surgically when feasible.⁠^[6]

Why not wait for the toe to fall off? In a small series of 12 people with diabetes and dry toe gangrene who were first watched, the toe separated by itself (autoamputation) in only one. Eight went on to surgical amputation, most of them major. The author favored early surgery but said waiting can still be tried cautiously, case by case; the series had no comparison group.⁠^[4] In the 100-patient review, people already acutely infected at surgery more often had slow healing, more operations or a higher amputation, and the authors suggested that removing stable gangrene earlier may help.⁠^[10]

Wet gangrene: urgent surgery

With severe artery disease, wet gangrene or a deep foot infection calls for urgent drainage and removal of dead tissue, including a minor amputation if needed, plus antibiotics.⁠^[2] For moderate and severe diabetic foot infections, surgery within 24 to 48 hours should be considered.⁠^[5] When circulation is also poor, the infection is controlled first; restoring blood flow is then considered within a few days, and a final operation may be needed to create a working foot.⁠^[1]

If a dark toe has redness, swelling or pus around it, or you have a fever or feel unwell, go to the emergency department. Dr. Ozturk performs the foot surgery these infections need: draining infection and removing dead tissue and infected bone. See diabetic foot infections and surgery for diabetic foot infection.

How surgery can save the foot

Minor amputations range from a toe or a ray (a toe with part of its metatarsal bone) to a transmetatarsal or midfoot (Lisfranc or Chopart) amputation. People with diabetes face a real chance of a later, higher amputation, yet these operations can keep the foot working for most.⁠^[2]

Swipe sideways to see the whole drawing.

Dr. Efe Ozturk is a Foot and Ankle Surgeon who is board certified in wound care (FAPWH). For the feet that need it, he performs toe, ray, transmetatarsal and midfoot amputations, choosing the level most likely to heal and keep you walking. If the wound can’t be closed after a small amputation, negative-pressure wound therapy can help it heal,⁠^[6] and a larger defect may be filled in and then covered with a skin graft.⁠^[2] We use these, and local flaps, for the wounds that need them. A below-knee amputation, if ever needed, is performed by a vascular or orthopedic surgeon. See toe and partial foot amputation and a second opinion before amputation.

Risks and limits. In the 46-study review, later major amputation ranged from 8% to 54% after transmetatarsal and 11% to 44% after midfoot amputations; across all levels, the review estimated that about 23% later needed a major amputation. Further minor amputation rates ranged from 12% to 33%, and slow healing and new ulcers were common, especially after transmetatarsal amputation.⁠^[8] That is why we plan follow-up, offloading and footwear from the start.

After healing: protecting the foot you have

Once the wound is closed, care shifts to keeping it closed: protective shoes and insoles, watching for warmth and redness, and long-term check-ups.⁠^[2] We offer risk-based check-ups, therapeutic shoes and custom inserts. With diabetes or blood vessel disease, check your feet routinely for injuries, color changes or signs of infection.⁠^[7] See problems after a partial foot amputation and our parent practice’s diabetic foot care (external site).

When to seek care

See us within a day or two for any foot wound that isn’t healing, especially if you have diabetes.