Critical limb ischemia (CLI) is the most severe form of peripheral artery disease (PAD), where blood flow to the leg or foot is critically reduced, even at rest. This severe lack of circulation leads to chronic pain, non-healing wounds, skin discoloration, or gangrene, and poses a serious threat to the limb.

CLI usually develops gradually as arteries supplying the leg become increasingly narrowed or blocked due to advanced atherosclerosis. Risk factors include diabetes, smoking, high blood pressure, high cholesterol, and a history of vascular disease. People with CLI may experience rest pain in the foot or toes, often worse at night, or they may notice ulcers or darkened areas of skin that do not heal.

If untreated, CLI can progress to tissue death (necrosis) and may require amputation. Prompt diagnosis is vital and often involves clinical examination, ankle-brachial index (ABI), Doppler ultrasound, and imaging studies such as CT or MR angiography.

Management typically focuses on restoring blood flow using angioplasty, stenting, or bypass surgery, along with medical therapy to improve circulation and address risk factors. Early intervention improves the chances of limb salvage and reduces the risk of life-threatening complications.