The concomitant occurrence of atherosclerotic peripheral vascular disease and peripheral neuropathy in patients with diabetes is the main factor in the development of diabetic foot pathology. Although neuropathy has proven the main risk factor for foot ulceration, peripheral arterial disease of the lower extremities is considered the major risk factor for lower-extremity amputation and it is also accompanied by a high likelihood for cardiovascular and cerebrovascular diseases (45). The rate of lower extremity amputation in the population with diabetes is 15 times that seen in the population without diabetes and within 4 years of the first amputation about 50% of contralateral limbs are lost (46,47). Life expectancy is also consistently reduced, as a result (48).
Although the underlying pathogenesis of atherosclerotic disease in diabetics is similar to that noted in nondiabetics, there are significant differences. As previously mentioned, diabetics have a fourfold higher prevalence of atherosclerosis, which progresses at a more rapid rate to occlusion. Patients with diabetes present with the sequelae of atherosclerotic disease at a significantly younger age than their counterparts without diabetes. Occlusive disease in patients with diabetes has a unique distribution, having the propensity to occur in the infrageniculate arteries in the calf. The typically affected arteries are the anterior tibial, posterior tibial, and peroneal. Equally important is the observation that the arteries of the foot, specifically the dorsalis pedis, are often spared of occlusive disease. This provides an excellent option for a distal revascularization target (49).
The clinical presentation of PVD in diabetes is also different because of the coexistence of peripheral neuropathy. In fact, while in patients without diabetes intermittent claudication—defined as pain, cramping or aching in the calves, thighs or buttocks that appears with walking exercise and is relieved by rest—is the initial presenting symptom, followed by rest pain, patients with diabetes might not complain of any ischemic symptom because of the loss of sensitivity or their symptoms can be confused with neuropathic pain. As a consequence, the development of tissue loss (foot ulceration or gangrene) might represent the first sign of lower limb ischemia and because of its limb-threatening potential, it is termed as critical limb ischemia. Therefore, patients with diabetes with a foot ulcer should always be evaluated for ischemia, irrespective of their symptoms, particularly for the increased risk of limb-threatening infection and faulty healing related to PVD (50).
The observations that pedal vessels are often spared from arterial occlusive disease had a crucial impact on the manner in which peripheral vascular disease is approached in the population with diabetes. In the past, based upon the false presumption of small vessel disease, diabetics were not treated as aggressively with revascularization as is now standard. A more aggressive attempt to correct the vascular deficit in diabetic ischemic limbs in addition to more aggressive measures to control local infection has radically altered the prognosis of peripheral vascular disease in the diabetic extremity.
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