In the general population, the most common cause of lower extremity ulcers is venous hypertension, and patients with diabetes, especially as they age, certainly can develop venous hypertension. Venous ulcers are often located above the medial or lateral malleolus and are usually painless. Clues to the diagnosis are frequently found in the surrounding skin and include edema, varicosities, stasis dermatitis, a yellow-brown discoloration due to hemosiderin, and induration of the skin as a result of lipoder-matosclerosis. However, in comparison to the general population, individuals with diabetes are more prone to the development of ulcers resulting from atherosclerosis and microangiopathy, peripheral neuropathy (mal perforans), necrobiosis lipoidica diabeticorum (NLD), calciphylaxis, and soft tissue infections.
In comparison to venous ulcers, arterial ulcers involve the toes and distal foot more frequently; they also favor the anterior tibial surface. Arterial ulcers are usually painful, especially at night, are often accompanied by claudication, and tend to have a "dry"
base. Clues to the diagnosis are found in the surrounding skin and include pallor, dry skin (xerosis), brittle nails, a decrease in the density of hair, and a shiny appearance to the skin (18). An examination for pallor with elevation and hyperemia with dependency can be performed, but an actual assessment of blood flow is essential. Following palpation of peripheral pulses, the ankle/brachial pressure index can be measured by Doppler, both at rest and following exercise. Radiographic studies are then performed to confirm the presence of surgically correctable disease. Therapeutic interventions include cessation of smoking, angioplasty, endarterectomy, and revascularization via bypass surgery.
Cholesterol emboli also can give rise to lower extremity ulcerations and represent yet another consequence of atherosclerosis. The resulting ischemia of the skin is reflected in angulated areas of blue to violet gray discoloration. Ulcerations as a result of calciphylaxis have a similar clinical appearance, and livedo reticularis (a blue to violet netlike pattern due to sluggish blood flow within the superficial venous plexus) often accompanies both entities. In patients with diabetes, the most common cause of calciphylaxis is secondary hyperparathyroidism in the setting of chronic renal failure.
The plantar surface of the foot is a very unusual location for an ulcer, and as a result, the possibility of a cutaneous malignancy such as a squamous cell carcinoma (e.g., epithelioma cuniculatum) or amelanotic melanoma is often entertained. However, in the presence of a peripheral neuropathy, the most likely diagnosis is a neuropathic ulcer or mal perforans. These ulcers are usually at the sites of greatest pressure and shearing forces (e.g., the metatarsal heads and heels). Clinically, there is often a thick keratotic rim surrounding the ulcer, and in order to heal a neuropathic ulcer, there must be a reduction in pressure via the use of orthotics, debridement, and exclusion of underlying osteomyelitis. Topical application of platelet-derived growth factor can also be added to the therapeutic regimen.
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