Leg ulcers refer to full thickness skin loss on the leg or foot due to any cause. They occur in association with a range of disease processes, most commonly with blood circulation diseases. Leg ulcers may be acute or chronic. Acute ulcers are sometimes defined as those that follow the normal phases of healing; they are expected to show signs of healing in less than 4 weeks and include traumatic and postoperative wounds. Chronic ulcers are those that persist for longer than 4 weeks and are often of complex poorly understood origin.
Ulcers may be provoked by injury or pressure such as from a plaster cast or ill-fitting ski boot. They may also be caused by bacterial infection, especially impetigo, ecthyma and cellulitis and less often tropical ulcer, tuberculosis or leprosy.
Chronic leg ulceration affects about 1% of the middle-aged and elderly population. It most commonly occurs after a minor injury in association with:
Chronic leg ulcers may also be due to skin cancer, which may be diagnosed by a skin biopsy of the edge of a suspicious lesion. There are also many less common causes of ulcers including systemic diseases such as systemic sclerosis, vasculitis and various skin conditions especially pyoderma gangrenosum.
Venous insufficiency refers to improper functioning of the one-way valves in the veins. Veins drain blood from the feet and lower legs uphill to the heart. Two mechanisms assist this uphill flow, the calf muscle pump which pushes blood towards the heart during exercise, and the one-way valves which prevent the flow of blood back downhill. There may be reflux through the valves, obstruction of the veins and/or impaired calf pumping action result in pooling of blood around the lower part of the leg to just below the ankle. The increased venous pressure causes fibrin deposits around the capillaries, which then act as a barrier to the flow of oxygen and nutrients to muscle and skin tissue. The death of tissue cells leads to the ulceration.
Arterial insufficiency refers to poor blood circulation to the lower leg and foot and is most often due to atherosclerosis. In atherosclerosis the arteries become narrowed from deposits of fatty substances in the arterial vessel walls, often due to high levels of circulating cholesterol and aggravated by smoking and high blood pressure (hypertension). The arteries fail to deliver oxygen and nutrients to the leg and foot resulting in tissue breakdown.
Diabetic ulcers are caused by the combination of arterial blockage and nerve damage. Although diabetic ulcers may occur on other parts of the body they are more common on the foot. The nerve damage or sensory neuropathy reduces awareness of pressure, heat or injury. Rubbing and pressure on the foot goes unnoticed and causes damage to the skin and subsequent ‘neuropathic’ ulceration.
Where possible, treatment aims to reverse the factors that have caused the ulcer. As ulcers are often the result of both arterial and venous disease, careful assessment is needed first.