Lower Extremity Arterial Disease

Key Points

  • Knowledge of normal and variant anatomy of the lower extremity arterial vasculature is critical.

  • A standardized and comprehensive duplex examination protocol is critical.

  • Knowledge of possible diseases/lesions potentially within the lower extremity arterial vasculature, and how to maximize their recognition, is critical.

This chapter is intended to review the ultrasound approach to assessment of arterial occlusive disease distal to the aorta. The arterial vasculature beyond the aorta has greater length than the aorta itself. As the arterial vasculature beyond the aorta involves progressively smaller and smaller vessels, it is more susceptible to occlusive disease than the aorta itself. Aneurysmal disease may occur at several levels in the lower extremity arterial vasculature. Duplex ultrasound of the lower extremity arterial vasculature is generally associated with noninvasive assessment of lower limb blood pressures, and may be associated as well with toe systolic blood pressure and transcutaneous oximetry.

Arterial Anatomy of the Lower Extremities

The anatomy of the arterial vasculature ( Figs. 5-1 to 5-3 ) of the lower abdomen, pelvis, and lower extremities is fairly consistent, with the level of branch origin being the most common type of variant. In 80% of cases, the aorta bifurcates within 1.25 cm of the iliac crest.

Figure 5-1

Arterial anatomy of the lower extremity.

(From Drake R, Vogl AW, Mitchell AWM. Gray’s Anatomy for Students. 2nd ed. Philadelphia: Elsevier; 2010; Figs. 6-36 and 6-48; used with permission.)

Figure 5-2

Arterial anatomy of the leg.

(From Drake R, Vogl AW, Mitchell AWM. Gray’s Anatomy for Students. 2nd ed. Philadelphia: Elsevier; 2010; Figs. 6-62 and 6-63; used with permission.)

Figure 5-3

Arterial anatomy of the foot.

(From Drake R, Vogl AW, Mitchell AWM. Gray’s Anatomy for Students. 2nd ed. Philadelphia: Elsevier; 2010; Figs. 6-117 and 6-118; used with permission.)

The right and left common iliac arteries are the continuation of the distal abdominal aorta at approximately the level of the fourth lumbar vertebra. The right and left common iliac arteries pass over the psoas muscle, run downward and laterally and themselves divide into internal (hypogastric) and external iliac arteries, the larger of the two branches, at a level between the last lumbar vertebra and the sacrum. The external iliac artery is larger than the internal iliac artery. The right common iliac artery is slightly longer than the left and passes over the fifth lumbar vertebra. There are small branches of the common iliac artery that supply the ureter, the peritoneum, and the psoas major muscle. Occasionally, accessory renal arteries arise from the common iliac artery.

Occlusion of the common iliac artery stimulates collaterals between branches of the abdominal aorta and the inferior mesenteric artery that bridge to the internal iliac artery and are thus one of the reasons that occlusive disease of the common iliac artery may be associated with bowel ischemia. Congenital atresia of one or both of the common iliac arteries is rare.

The external iliac artery has several small branches, which supply the psoas major muscle and lymph glands and two larger branches that arise from its distal segment. The first branch is the deep circumflex artery, which arises from the lateral surface of the external iliac artery and courses toward the anterior superior iliac spine, where it joins with branches of the lateral femoral circumflex artery. This connection is an important collateral source when common iliac artery occlusion extends into the internal iliac artery. The second branch of the external iliac artery is the inferior epigastric branch, which arises medially almost opposite the deep circumflex artery and courses superiorly beneath the rectus abdominis muscle.

In external iliac or common femoral artery occlusion, collateral vessels form between the gluteal branches of the internal iliac artery and the femoral circumflex branches of the profunda femoris artery.

The internal iliac artery, on average 4 cm long and with highly variable branching patterns, arises opposite the lumbosacral articulation and courses downward and medially with branches that supply the buttock, walls and viscera of the pelvis, reproductive organs, and medial side of the thigh.

The common femoral artery is a continuation of the external iliac artery. It originates at the inguinal ligament and is part of the femoral sheath, a downward continuation of the fascia lining the abdomen, which also contains the femoral nerve and vein. The common femoral artery extends approximately 3 to 4 cm below the inguinal ligament, where it then bifurcates into the superficial femoral and profunda femoris artery.

The profunda femoris artery, which lies lateral to the superficial femoral artery, gives rise to segmentally occurring circumflex and perforating branches which, when the superficial femoral artery is occluded, connect with the genicular branches of the popliteal artery to reconstitute the distal segment at the level of the adductor hiatus.

Clinical Pearls

  • Even when the Doppler angle of insonation is inappropriate for acquisition of accurate velocity measurements, for example along the mid-external iliac artery where its course is parallel to pelvic floor, a suitably steered color box still reveals a focal narrowing by depicting turbulent flow and thereby gives some indication of the presence of stenosis.

  • If a lower foreleg artery (such as the tibial artery) is subtotally occluded, its ongoing segments may be mistaken for the accompanying vein, as they may be easily comprensible, due to low distending pressure, against shallowly underlying bone.

  • A triphasic nonturbulent waveform at the common femoral level does not necessarily mean that there is no significant stenosis in either the common or external iliac arteries.

  • At the femoral bifurcation, the profunda femoris artery may sometimes run in the usual position of the superficial femoral artery (i.e., more anteriorly for the first few centimeters) and the superficial femoral artery run more posteriorly. Hence, the vessels need to be followed along their length to identify them, and their courses may be atypical and engender confusion as to their identify. In a slim leg, this could result in the impression that the vessel is occluded by the time the mid thigh is reached and the profunda femoris artery had devolved into smaller branches.

  • In a situation where the superficial femoral artery is chronically occluded and its ultrasonographic appearance blends into the surrounding tissues, it is possible to follow the profunda femoris artery until it divides into branches, giving the impression that the vessel is at least patent in the proximal thigh.

  • A saphenous vein bypass graft typically lies closer to the skin surface than does the native vessel and is therefore more likely to be easily compressed by the probe during scanning, falsely suggesting narrowing. Hence when scanning, use very light pressure and lots of gel.

  • Biphasic (increased diastolic) flow rather than the usual triphasic flow can be seen in the periphery of normal arteries when there is vasodilation and hyperemia as a result of infection, for example.

From the femoral bifurcation, the superficial femoral artery continues as the primary conduit between the common femoral and popliteal artery, giving off several small branches along its course and from the mid- to distal thigh, running under the sartorius muscle in the adductor canal along with the femoral vein and branches of the femoral nerve.

In the distal thigh, the superficial femoral artery courses deeply through the adductor hiatus and posteriorly into the popliteal fossa, to become the popliteal artery.

There are three groups of branches of the popliteal artery: (1) the genicular arteries, which form a collateral network around the knee; (2) the paired sural arteries, which arise from the posterior aspect and supply the gastrocnemius and soleal muscle; and (3) the anterior tibial artery, which crosses the upper edge of the interosseous membrane and extends down to the level of the medial malleolus.

The genicular branches connect with tibial branches to form a collateral network and bypass popliteal artery occlusions.

The tibioperoneal trunk extends approximately 2.5 cm from the takeoff of the anterior tibial artery to the bifurcation of posterior tibial and peroneal arteries, with the posterior tibial running distally to a point midway between the medial malleolus and the tip of the heel.

A common variant of anatomy is a small or absent posterior tibial artery, which is frequently diminished in size and absent in approximately 5% of limbs individuals (bilaterally). The peroneal artery is typically larger when the posterior tibial artery is small or absent.

There is generally a dearth of collateral availability and formation in the foreleg. Because there are few branch vessels present in the proximal foreleg to participate as collaterals, occlusion of the popliteal and proximal tibial arteries may result in severe distal ischemia.

The peroneal artery originates from the bifurcation of the tibioperoneal trunk and descends along the medial side of the fibula. The peroneal artery bifurcates behind the lateral malleolus into the lateral calcaneal arteries and may provide large collateral branches to the tibial arteries in the distal calf.

The dorsalis pedis artery is the continuation of the anterior tibial artery and runs lateral to the extensor tendon to the first toe. The line of demarcation of the two is held to be the level of the ankle. The artery is congenitally absent in approximately 4% to 5% of individuals but always bilaterally. In approximately 4% of individuals, the dorsalis pedis artery is a continuation of the perforating branch of the peroneal artery, and the anterior tibial artery does not extend to the ankle level or it is severely diminished in size. This variant artery may be detected by duplex scanning, and unless the anterior tibial artery is mapped, its continuation from the anterior tibial artery may be wrongfully assumed. As with the arteries within the hand, an arcade of vessels provides redundancy and digital branches.

The figures in this chapter represent numerous examples of ultrasound scanning of lower extremity arteries: common femoral artery ( Figs. 5-4 to 5-7 ), superficial femoral artery ( Figs. 5-8 to 5-15 ), profunda femoris artery ( Figs. 5-16 and 5-17 ), common iliac artery ( Figs. 5-18 to 5-28 ), external iliac artery ( Figs. 5-29 to 5-33 ), internal iliac artery ( Fig. 5-34 ), popliteal artery ( Figs. 5-35 to 5-40 ), surgical cases ( Figs. 5-41 to 5-48 ), and trifurcations ( Figs. 5-49 to 5-52 ).

Figure 5-4

Stenosis of the common femoral artery by grayscale and color flow mapping is less than 50%. Spectral display of the flow before the plaque ( left ) and at the plaque ( right ) does not reveal an acceleration. The color Doppler flow pattern also does not show turbulence.

Figure 5-5

The grayscale image reveals the plaque in the common femoral artery. Spectral flow display reveals turbulence, but flow velocity is within the normal range. Without determining the flow velocity before the plaque, an acceleration of flow cannot be excluded.

Figure 5-6

False aneurysm arising from the common femoral artery post–coronary angiography. The short tract and body are seen on color Doppler flow mapping. The reciprocating flow pattern is depicted by spectral display.

Figure 5-7

Severe stenosis of the common femoral artery. Top left and right, Color Doppler aliasing and reverberation into the tissues is seen. Middle left and right, Images confirm a systolic velocity ratio greater than 4 and considerable poststenotic turbulence consistent with stenosis. Bottom left and right, Computed tomography angiography images reveal heavy calcification of the common femoral arteries that on the right side obscures the underlying stenosis.

Figure 5-8

Stented superficial femoral artery. Left, On grayscale imaging, the stent is barely apparent. As the underlined atheromatous plaque is fairly homogenous, it is also barely visible. Right, The spectral flow pattern and velocities are normal.

Figure 5-9

Occlusion of the superficial femoral artery. Top left, Color flow mapping at the level of occlusion of the superficial femoral artery. Abrupt cessation of flow is depicted with stem vessels, appearing blue by color Doppler flow mapping. Top right, A few centimeters more distally, no flow can be detected by color Doppler flow mapping. Bottom left, Flow cannot be detected by power angiography flow mapping. Bottom right, Further distally, color Doppler flow mapping at the far end of the occlusion demonstrates flow that seems to be reversed due to the inflow through reconstituting reentry vessels distally.

Figure 5-10

A greater than 50% stenosis of the superficial femoral artery. Top left, Grayscale imaging of the superficial femoral artery shows a tapering soft tissue linear lesion projecting into the lumen that was seen to have slight motion on real-time imaging. Top right and bottom left, Color Doppler flow mapping at this level more clearly shows the tapered shelflike lesion. This patient had a patent femoro-femoral bypass graft. Bottom right, The spectral Doppler waveform suggests that perhaps the graft is “stealing” flow from the artery here because the narrowed flow stream is not accompanied by high-velocity flow as would be expected and the flow pattern is tardus parvus and bidirectional (the shape of a “stealing” waveform).

Figure 5-11

A, Embolic occlusion of the superficial femoral artery. Top left, Grayscale imaging reveals homogenous material filling the distal superficial femoral artery. Top right, Power angiography Doppler cannot delineate any flow within the popliteal artery. Middle left, There is abrupt termination of flow in the proximal superficial femoral artery. Middle right, Again, abrupt termination of flow seen in the proximal right superficial femoral artery with flow still in the profunda femoris artery. Bottom left, Blunted flow pattern proximal to the occlusion. Bottom right, No detectable flow by spectral display. B, Electrocardiogram revealing atrial fibrillation, the source of the occlusive embolus to the superficial femoral artery and popliteal arteries.

Figure 5-12

Three-dimensional reconstructions of a computed tomography aortogram. Abrupt occlusion of a right superficial femoral artery is seen due to embolization.

Figure 5-13

Bilateral superficial femoral artery aneurysms, both of which contain mural thrombus.

Figure 5-14

Long-standing stenosis of the superficial femoral artery (SFA) with large collaterals. Top left, A large collateral vessel arising from the SFA. Top right, Narrowing of the SFA after the collateral branch takeoff, turbulence at the site of narrowing, and other deeper collaterals. Bottom left and right, Spectral display of pulsed Doppler sampling before, and at the site of turbulence, with a significant velocity ratio consistent with stenosis.

Figure 5-15

Small false aneurysm arising out of the superficial femoral artery. The flow pattern is the typical reciprocating flow seen in the tract between artery and pseudoaneurysm.

Figure 5-16

Occlusion of the profunda femoris artery. Left, The color Doppler flow mapping does not record flow at one level. Right, Immediately distal to the spectral flow recording is reconstitution via reentry vessels—hence the reversed flow component, which is also apparent on the color Doppler flow mapping.

Figure 5-17

Significant stenosis at the ostium of the first branch profunda femoris artery. Left, Color Doppler flow mapping reveals turbulence at the ostium. The responsible plaque is not easily seen on the grayscale imaging. Right, The spectral display demonstrates significant increase in velocity consistent with greater than 50% stenosis.

Figure 5-18

Less than 50% stenosis of the common iliac artery. Top left, Grayscale imaging reveals plaque that appears to be less than 50%. Top right, Color Doppler flow mapping depicts turbulence and acceleration of the site of the plaque. Bottom left and right, Spectral flow display before ( left ) and at the site of stenosis ( right ) reveals a less than 100% increase in velocity. Notably, there is variation for the peak systolic velocity in the samplings before and at the site of the stenosis, conferring some uncertainty as to the stenosis severity determination on the basis of the velocity ratio.

Figure 5-19

Longitudinal ( left ) and cross-sectional ( right ) views of a 3-cm tubular aneurysm of the common iliac artery.

Figure 5-20

Dissection of the common iliac artery. Top left and right, Grayscale longitudinal ( left ) and cross-sectional ( right ) images demonstrate the intimal flap and resultant true and false lumen within the iliac artery. Bottom left , Color Doppler flow mapping reveals partitioning flow by the intimal flap and flow both in true and false lumens. Bottom right, There is notable complexity of the intimal flap at one portion along the artery.

Figure 5-21

Bilateral aneurysms of the common iliac arteries.

Figure 5-22

Views of the common iliac artery following stenting. In this case the stent is not visible, although the large volume of atherosclerotic plaque that has been responsible for the stenosis is apparent. Poststenting flow pattern and flow velocities are normal.

Figure 5-23

Iliac artery to vein fistula. An aneurysm of the iliac artery has ruptured into the adjacent vein.

Figure 5-24

Ostial stenosis of the right common iliac artery. Left, Flow recorded in the distal abdominal aorta is of normal velocity and contour. Right, At he ostium of the right common iliac artery, color Doppler flow mapping depicts turbulence, and spectral display depicts velocities that are both elevated in the absolute sense and also elevated when compared with the upstream velocity within a distal aorta.

Figure 5-25

Greater than 50% stenosis of the common iliac artery. Left, Color flow mapping revealing acceleration and turbulence within the common iliac artery and spectral flow display revealing severely elevated systolic velocities. This is as well “color bruit” and “spectral bruit.” Right, The velocity is almost normalized several centimeters downstream, but turbulence persists.

Figure 5-26

Fifty percent stenosis of the common iliac artery. Color Doppler flow mapping is consistent with acceleration and turbulence, and spectral display reveals significant increase (>100%) from before the site of stenosis ( left ) to the site of stenosis ( right ).

Figure 5-27

Severe stenosis of the right common iliac artery. Left, Systolic flow velocity in the left common iliac artery is in the normal range, although the early diastolic flow reversal component is absent. Right, Color flow aliasing is accompanied by severely elevated systolic flow velocity, although waveform morphology still suggests biphasicity.

Figure 5-28

Atherosclerotic ectasia (irregularity and tortuosity, and also dilation in this case) of the common iliac artery.

Jun 30, 2019 | Posted by in ULTRASONOGRAPHY | Comments Off on Lower Extremity Arterial Disease
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