Critical Limb Ischemia (Chronic Limb-Threatening Ischemia)

How critical limb ischemia develops

Atherosclerosis (fatty plaque buildup) narrows the arteries supplying the legs, a condition called peripheral artery disease (PAD). Early PAD may cause no symptoms or calf pain when walking (claudication). As narrowing worsens and multiple segments are blocked, blood flow becomes too low even for the resting needs of the foot. Tissues starve of oxygen, causing pain, ulcers and tissue death.

Diabetes and chronic kidney disease cause blockages in the smaller arteries below the knee, which are harder to treat.

Symptoms

• Rest pain: burning or aching in the toes or forefoot, worst at night when lying flat. Hanging the foot over the edge of the bed or sleeping in a chair brings relief because gravity helps blood flow
• Non-healing wounds: sores on toes, heels or the sides of the foot that do not heal in 2 weeks or more
• Gangrene: dry, black, shriveled tissue, usually starting at the toes
• cold, pale feet that turn red when hanging down (dependent rubor)
• shiny, thin skin, hair loss on the legs, thick toenails
• weak or absent foot pulses
• numbness and muscle wasting

People with diabetic nerve damage may feel little pain, so wounds can be the first sign.

Risk factors

• smoking, the strongest modifiable risk factor
• diabetes
• chronic kidney disease, especially on dialysis
• high blood pressure and high cholesterol
• age over 65
• existing heart or cerebrovascular disease

Diagnosis

1. Ankle-brachial index (ABI): compares blood pressure at the ankle with the arm. Values below about 0.4 suggest severe disease. In diabetes and kidney disease, calcified arteries can give falsely normal readings.
2. Toe pressures and toe-brachial index, and transcutaneous oxygen measurements, which better reflect blood flow to the foot.
3. Duplex ultrasound to map narrowing.
4. CT angiography or MR angiography to plan treatment.
5. Catheter angiography, often combined with treatment.

The WIfI system (Wound, Ischemia, foot Infection) grades limb threat and guides decisions.

Treatment

Revascularization

Restoring blood flow is the key to saving the limb.

• Endovascular treatment: balloon angioplasty, stents or atherectomy through a small puncture, usually in the groin. Less invasive, with quicker recovery.
• Bypass surgery: using a vein (preferred) or synthetic graft to route blood around the blockage. Better long-term durability in some patients, particularly those with a good vein and longer life expectancy.
• Hybrid procedures combine both.

The choice depends on the pattern of disease, available vein, wound severity and overall health.

Wound and foot care

• regular cleaning and dressings
• removal of dead tissue, and minor amputation of toes if needed
• treating infection with antibiotics and drainage
• offloading pressure with special footwear
• specialist multidisciplinary foot teams improve limb salvage

Medicines and risk factors

• stopping smoking
• antiplatelet therapy (aspirin or clopidogrel), sometimes with low-dose rivaroxaban after revascularization
• high-intensity statins
• blood pressure and blood sugar control
• pain relief

Amputation

When blood flow cannot be restored, infection is life-threatening, or the foot is not salvageable, amputation relieves pain and can restore mobility with a prosthesis.

Outlook

CLI is a marker of widespread artery disease. Without revascularization, many people lose a limb within a year. Patients also have high rates of heart attack and stroke, so treating cardiovascular risk is as important as treating the leg. With successful revascularization, wound care and risk factor control, many limbs are saved.

Prevention

• do not smoke
• control diabetes, blood pressure and cholesterol
• walk regularly, which improves circulation in early PAD
• check your feet daily if you have diabetes or PAD, and report wounds early
• have PAD symptoms like claudication assessed before they progress

Frequently asked questions

What are the symptoms of critical limb ischemia?

Key symptoms are burning pain in the toes or foot at rest, especially at night and relieved by hanging the leg down, wounds on the feet that do not heal, and black or dying toes. The foot may be cold, pale and lack pulses.

Is critical limb ischemia an emergency?

It needs urgent specialist assessment, usually within days, because limbs can be lost without treatment to restore blood flow. A sudden cold, painful, pale or numb leg is a separate emergency (acute limb ischemia) and needs immediate care.

Can critical limb ischemia be reversed?

Restoring blood flow with angioplasty, stents or bypass surgery can relieve rest pain and allow wounds to heal, saving the limb in many cases. The underlying artery disease remains, so lifelong medicines, not smoking and regular follow-up are needed.

What is the life expectancy with critical limb ischemia?

It varies widely. CLI indicates severe, widespread artery disease, and many people also have heart disease, diabetes or kidney disease. Studies show substantially higher mortality than in the general population, which is why controlling cardiovascular risk is vital.

How is critical limb ischemia different from claudication?

Claudication is leg pain during walking that stops with rest, an earlier stage of peripheral artery disease. Critical limb ischemia causes pain even at rest, non-healing wounds or gangrene, meaning blood flow is too low to keep tissue alive.