Critical limb ischemia (CLI), also referred to as limb threat, is an advanced stage of peripheral artery disease. It is defined as a triad of ischemic rest pain, arterial insufficiency ulcers, and gangrene. The latter two conditions are jointly referred to as tissue loss, reflecting the development of surface damage to the limb tissue due to the most severe stage of ischemia. CLI has a negative prognosis within a year after the initial diagnosis, with 1-year amputation rates of approximately 12% and mortality of 50% at 5 years and 70% at 10 years.
CLI was conceived to identify patients at high-risk for major amputation, but the increasing prevalence of diabetes mellitus has led to a broader conception of limb threat that includes the risk of amputation associated with severely infected and non-healing wounds.