LOWER EXTREMITY VASCULAR INSUFFICIENCY
Vascular insufficiency of the lower extremity is a common finding in the older population. Factors that increase the risk of vascular disease include diabetes, obesity, smoking, hypertension, and hypercholesterolemia. Both the venous and the arterial systems may be affected, and the signs and symptoms are unique to each. The combination of venous and arterial insufficiency is commonly seen in older diabetic patients, especially those who smoke. Abnormalities of the lymphatic system may cause findings similar to those of venous insufficiency. Risk factors for lymphatic disease include prior surgeries (e.g., inguinal lymph node dissection), radiotherapy, and idiopathic lymphedema.
Clinical Findings: Venous insufficiency is a common disease that has no racial or ethnic predilection. It has been reported to be slightly more common in women. Venous insufficiency eventually leads to venous stasis and ulcerations. It has been estimated to be the cause of more than 50% of lower extremity ulcerations, with arterial insufficiency being the next most common cause, and neuropathic causes and lymphedema accounting for the remainder.
The first signs of venous insufficiency may be the development of varicose veins or smaller dilated reticular veins. As time progresses, venous stasis changes are seen, including dry, pink to red, eczematous patches with varying amounts of peripheral pitting edema. Red blood cells are extravasated into the dermis where, over time, they break down and form hemosiderin deposits, which appear as brown to reddish macules and patches. Continued venous hypertension, stasis, and swelling may eventually lead to a venous stasis ulcer. These ulcers are most commonly present on the medial malleolus region of the ankle but can occur almost anywhere on the lower extremity. They are usually nontender, but some can be exquisitely painful. Arterial insufficiency is most often caused by atherosclerosis of the larger arteries of the lower extremity. Patients often have coexisting risk factors including older age, hypertension, smoking, diabetes, and hyper-cholesterolemia. Arterial ulcers are slightly more common in men, and there is no racial predilection. The clinical presenting signs are often dependent rubor, claudication, and rest pain. Physical examination confirms the absence of peripheral pulses in the dorsal pedal and posterior tibial arteries. At this point, the patient is at high risk for arterial ulcerations and subsequent gangrene. Surgical intervention is the only viable means of treatment.
Pathogenesis: Venous drainage of the lower extremity is accomplished via the superficial and deep systems of veins that are connected through horizontally arranged communicating vessels. These veins contain one-way bicuspid valves that prevent backflow and work with the action of muscle contraction to force the venous flow in a superior direction, eventually to empty into the inferior vena cava. The flow of venous blood toward the vena cava is the primary responsibility of the leg muscles, especially the calf muscle. Patients with sedentary lifestyles are at higher risk for venous insufficiency. During ambulation, the venous pressure normally decreases as the blood flow is increased toward the vena cava. If an abnormality exists and this does not occur, venous hypertension ensues. Congenital absence of the venous valves, incompetent valves, and a history of deep venous thrombosis are just three of the potential reasons for venous insufficiency. Once venous hypertension occurs, the patient is at risk for development of venous stasis and venous ulcerations.
Arterial insufficiency is caused by a slow narrowing of the arteries due to cholesterol plaque. This narrowing restricts the amount of blood flow to the tissue. Once the flow is decreased to less than the requirement needed for muscle and normal physiological functioning, symptoms arise.
Histology: Biopsies should not be performed in cases of arterial insufficiency, because they lead to ulcerations, infections, and, most likely, emergent surgery.
Histological evaluation of venous ulcerations shows a nonspecific ulcer, edema, proliferation of superficial dermal vessels, and extravasated red blood cells with a varying amount of hemosiderin deposition.
Treatment: Venous insufficiency is treated with a combination of compression and leg elevation. Losing weight and increasing the activity level may also help. Arterial insufficiency is best treated surgically with stent placement or arterial bypass of the narrowed artery. Pentoxifylline has also been used, with variable success, in early disease.