PERIPHERAL ANEURYSMS AMD FISTULAE



Occasionally true or false aneurysms may occur in peripheral vessels. True aneurysms are usually secondary to atherosclerosis; false aneurysms (i.e., a tear in the arterial wall allowing accumu­lation of blood in the perivascular tissues) may be associated with trauma or rupture of a true aneu­rysm. True aneurysms of peripheral vessels are located most commonly in the popliteal artery but can occur in the femoral artery, iliac artery, ar­teries of the upper extremities, and occasionally visceral arteries such as renal or splenic arteries. Aneurysms of the popliteal and femoral arteries are often palpable. Aneurysms may occasionally be infected (mycotic). Symptoms result from ar­terial occlusion, rupture, distal embolization, or local pressure on adjacent structures such as nerves or veins. Surgery for renal or splenic artery aneurysms is usually recommended in patients who are pregnant (increased incidence of rupture) or whose aneurysm is symptomatic, enlarging, or more than 1.5 to 2.0 cm in diameter. Femoral and popliteal aneurysms should be treated surgically if the patient’s condition allows.

Arteriovenous fistulae are acquired or congen­ital abnormal communications between arteries and veins without an intervening capillary net­work. Acquired fistulae may be created to facili­tate hemodialysis or may occur after trauma such as a gunshot or stab wound. Increased blood flow leads to venous dilation and makes the region of the fistula abnormally warm; the area distal to the fistula may be cool. If the fistula is large, a high cardiac output state may occur and may produce heart failure. Because of the low resistance path­way, diastolic blood pressure tends to decrease, and systolic blood pressure and pulse pressure in­crease. A bruit and thrill may be present over the fistula. If the artery serving the fistula is com­pressed, shunting via the low resistance circuit is prevented, and a prompt decrease in the pulse rate may occur (Branham’s sign). Acquired fistulae are best treated surgically. Congenital AV fistulae are usually multiple, small, and often accompanied by cutaneous birthmarks. Enlargement of the en­tire involved limb may occur, since the fistulae are present during the period of rapid bone growth. Bruits and pulsatile masses are uncom­mon, since the fistulae are small and multiple. Treatment is less satisfactory than that of large acquired AV fistulae.