Peripheral Vascular Disease

Peripheral Vascular Disease

Atherosclerotic vascular disease is probably present (at least in a subclin- ical form) in all patients with long-duration diabetes. Like other forms of macrovascular disease, peripheral vascular disease (PVD) is more common in diabetes. Using clinical techniques of palpation of foot pulses, the Framingham Study found a 25–50% excess of PVD in people with diabetes, but using Doppler pressures, PVD can be found in up to 3 times as many diabetic as nondiabetic people.

The distribution of vascular disease in the lower limb is thought to be different in diabetes, with more frequent involvement of vessels below the

knee. This is somewhat similar to the distal pattern of disease that is often seen in the coronary circulation, and may partly explain the fact that PVD is frequently asymptomatic in people with diabetes, and may present with is- chaemic foot ulceration or gangrene, with no previous claudication. Distal disease may allow a reasonable blood supply to be maintained to the large muscles involved in walking, whilst critically impairing the supply to the skin of the feet. Co-existent neuropathy and exercise limitation due to other diseases may also mask the symptoms of PVD. Thus, regular screening by physical examination is necessary to identify people with PVD.

Although PVD is more prevalent amongst the diabetic population, once established it does not progress any more rapidly than does PVD in the nondiabetic population. Furthermore, its treatment should follow similar lines. Exercise can improve claudication distances, and revascularization procedures are frequently successful, although may require a more distal anastomosis.

In the pathogenesis of diabetic foot ulcers, ischaemia is a major factor in

a third to a half of all cases, and approximately 50% of amputations can be attributed to ischaemia. In a prospective study of type 2 diabetes, PVD (mea- sured by Doppler techniques) nearly doubled the risk of developing a foot ulcer – an effect that was independent of a wide range of other risk factors.

Diabetic Neuropathy

Somatic Neuropathy Chronic sensorimotor peripheral neuropathy is one of the commonest

long-term complications of diabetes affecting at least a third of older diabetic patients in the UK according to a large study of hospital outpatients. Its onset

is insidious and data suggest that only about a third of patients with objective evidence of neuropathy actually have neuropathic symptoms. Thus progression to the insensitive foot at high risk of ulceration can occur without the patient being aware of any disorder. Identification of the neuropathic foot at risk of ulceration therefore relies on careful examination.

Typically, the sensory defect predominates, but a motor component is often present, and its distal nature leads to small muscle wasting in the foot with a consequent imbalance of flexor and extensor muscles resulting in clawing of the toes and prominence of the metatarsal heads, which then become potential sites of ulceration.

Peripheral somatic neuropathy has been clearly associated with foot ul- ceration in several cross-sectional and prospective studies. The risk of ulcera- Peripheral somatic neuropathy has been clearly associated with foot ul- ceration in several cross-sectional and prospective studies. The risk of ulcera-

Autonomic Neuropathy Sympathetic dysfunction affecting the lower limbs leads to reduced sweat-

ing and results in dry skin that is prone to crack and fissure. It also increases blood flow (in the absence of large vessel PVD) with arteriovenous shunting leading to the warm foot. The insensitive foot is therefore often warm resulting in a false sense of security, as the patient perceives that because the circulation is intact, the risk is minimal.