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ab c
2.1 · Pelvic andLeg Arteries
. Fig. 2.21a–c Grading of high-grade stenosis. a Hypoechoic plaque (P) causes high-grade stenosis with a PSV of almost 4m/s and mono-
phasic ow. Similar constellation as in . Fig.2.20, except that the stenosis is high-grade. b Continuous spectral Doppler imaging as described
in . Fig.2.20 reveals an increase in PSV from 60cm/s to over 3m/s in the stenosis, corresponding to a PSV ratio>4, which indicates high-grade
stenosis. c Angiogram conrms high-grade stenosis of the supercial femoral artery
83
forms from the proximal and distal segments (e.g., tibiobular
trunk or proximal anterior tibial artery and main artery at
ankle level; see
. Figs.2.68 and 2.69 (both Atlas)). Use of the
indirect stenosis criteria discussed above can also facilitate
and shorten the sonographic examination of the calf arter-
ies, which are less amenable to ultrasound evaluation
. e
search for steno-occlusive lesions or the evaluation of potential bypass targets below the knee begins with a Doppler
interrogation of the dorsalis pedis and posterior tibial arteries. e Doppler waveforms from these sites are compared
with a waveform from the popliteal artery. e examiner
then proceeds to obtain Doppler waveforms from the proximal calf arteries for comparison with the waveforms from the
ankle area to narrow down sites of obstruction. Finally, if
relevant for treatment planning, the examiner can try and
. Fig. 2.22 Stenosis of the anterior tibial artery (at mid-calf level)
with an intrastenotic PSV of 209cm/s. Due to wide interindividual
variation in blood ow velocities below the knee, absolute PSV is no
valid criterion for stenosis grading in this territory. The PSV ratio (calculated from 209cm/s within the stenosis (right portion of waveform)
and 36cm/s in the prestenotic segment (left portion of waveform)) is
>5, corresponding to >80% stenosis
localize individual lesions (stenosis or occlusion). If the calf
arteries are examined to identify the site of distal anastomosis for a crural bypass gra once occlusive disease of the popliteal artery and trifurcation has been conrmed, the
examiner rst identies the artery with the highest blood
ow in the ankle area. is artery is then continuously
scanned from the ankle upward using low-ow settings to
collateral artery bridging an occluded segment is less pulsatile because peripheral resistance is decreased. In this situation, only an increase in absolute PSV above a threshold
(dened by comparsion with angiography) and a monophasic ow prole are valid criteria for diagnosing a stenosis.
detect the slow ow in the calf arteries (similar to venous
ow), searching for lesions that might preclude its use as a
bypass target and identifying the most suitable site for the
distal anastomosis. At the same time, the candidate artery is
screened for a greater than 100% increase in PSV, which indicates a hemodynamically relevant stenosis (. Fig.2.24), even
2.1.6.1.10 Spectral Doppler Imaging below
theKnee
Normal peak systolic velocity (PSV) decreases as one progresses down the leg (. Table2.5), and there is wide interindividual variation in PSV in the arteries below the knee. is
is why no absolute PSV cutos for diagnosing hemodynamically relevant stenosis (>50%) or higher-grade stenosis in this
segment have been identied by ROC analysis. Instead,
intrastenotic-to-prestenotic PSV ratios should be calculated
for stenosis grading below the knee (. Fig.2.22).
e site of occlusion in a below-knee artery can be nar-
rowed down by analyzing and comparing Doppler wave-
in vessel segments distal to an occlusion, possibly rendering
it unsuitable for use as a bypass target.
Ultrasound examination of the arteries below the knee
is limited
in patients with extensive atherosclerotic disease or
longstanding diabetes with severe medial sclerosis. In these
patients, calcied lesions may produce acoustic shadowing,
precluding long segments of the arteries from being evaluated for the presence of stenosis or occlusion. When acoustic
shadowing occurs, stenosis grading becomes inaccurate and
the length of an occluded segment can be misinterpreted.
Acoustic shadowing is a problem that cannot be overcome by
the use of ultrasound contrast agents. Good knowledge of the
2
84
bc
Chapter 2 · Extremity Arteries
2
a
d e
. Fig. 2.23 a Sonographic examination of the bular artery in a patient with a long history of diabetes mellitus and popliteal artery occlusion.
Hardly any ow signals are apparent in the color ow image (despite adequate PRF and gain settings). In such a situation, it is often possible to
demonstrate ow in a spectral tracing recorded with higher gain; in the example the waveform shows postocclusive ow. It is also helpful to
overmodulate receive gain (artifacts in waveform). b Color ow image (nearly identical view) after echo enhancer administration shows ow
almost throughout the artery. Contrast-enhanced ultrasound (CEUS) with a low mechanical index (MI) is not helpful because even simultaneous B-mode imaging often fails to provide adequate resolution for sonoanatomic identication of the arteries below the knee (see . Figs.2.70
(Atlas), 5.19, and 5.59 (Atlas)). Therefore, it is recommended to perform CEUS using the conventional color duplex mode (without lowering
transmit gain). Great care is necessary to accurately identify the main arteries sonoanatomically and avoid the pitfall of mistaking a collateral with
good color lling for a patent main artery. c, d, e The distal bular artery is patent but multiple focal stenoses (with PSV ratios up to 2, consistent
with <50% luminal narrowing) are noted in this segment. For illustration, the examples show an increase in PSV from 12cm/s (c) to 36cm/s (d),
corresponding to approx. 60% stenosis. Because the distal bular artery is imaged approx. 45s after injection of the echo enhancer (and the
microbubbles are rapidly destroyed due to the use of normal transmit gain), the enhancing eect is already fading and there is poorer color lling. Overall, the examination reveals no higher-grade stenosis, suggesting that the bular artery is a suitable recipient vessel for a bypass graft. A
stenosis below the knee identied by CEUS can be graded using the PSV ratio. In the case presented here, the angiogram (e) conrms the bular
artery to be the only patent major artery below the knee and to be suitable to receive a bypass graft. Color duplex ultrasound often allows better
stenosis grading based on the PSV ratio than survey angiograms based on morphology (which tend to be degraded by poor opacication distal
to an occlusion)
sonoanatomy of the calf vessels is important to accurately
assess vascular disease in this territory and to minimize the
risk of misinterpretation that may result from mistaking a
collateral for a main calf artery.
2.1.6.1.11 Role ofContrast-Enhanced Ultrasound
Contrast-enhanced ultrasound (CEUS) of the peripheral arteries may be helpful in patients with poor insonation conditions
or for better detection of slow-ow or low-ow states. An example is the evaluation of the arteries below the knee to search for
additional steno-occlusive lesions in patients with proximal
occlusion, which may be indicated to identify a patent crural or
pedal target artery for bypass graing. A full CEUS evaluation
of the arteries below the knee may require repeated injection or
continuous infusion of contrast microbubbles to ensure adequate enhancement throughout the examination. is is necessary because the image quality of B-mode imaging with low
mechanical index (MI), which is normally used for CEUS to
delay destruction of the microbubbles, is too poor for this vascular territory. Performing CEUS with standard power output
(7 Sects. 1.1.5 and 6.1.2.1.2; . Fig. 2.70 (Atlas)) requires
repeated administration of smaller doses to compensate for
rapid microbubble desctruction (. Fig.2.23b, c). Injection of a
larger dose or rst-pass imaging does not overcome this problem because it is associated with color blooming, which
obscures the vessel wall. Shortly aer injection, dilution of the
microbubbles results in good color lling of the lumen.
Conversely, if the dose is too low, there will be poor color lling
of the patent lumen.
Few scientic data are available on how contrast agents
can improve the sonographic diagnosis. In a small study of 14
patients, Ubbink etal. (2002) found diagnostic condence to
increase from 56% to 91% aer contrast administration compared with standard color duplex ultrasound in postocclu-
sive below-knee arteries
(poor visibility, slow ow, low
ow) (. Fig.2.23). In a multicenter study including a total of
82 patients (Sidhu etal. 2006), the percentage of poorly visualized vascular segments was found to decrease from 40.7%
to 7.4% when SonoVue was given at a dose of 2.4mL.A subgroup analysis of agreement with dierent reference methods
(angiography, CT angiography, magnetic resonance imaging) showed that the diagnostic accuracy of color duplex
2.1 · Pelvic andLeg Arteries
85
2
imaging increased from 30.7% to 68.9% aer administration
of the contrast agent. A limitation of this study is the use of
dierent ultrasound equipment and the diversity of vascular
territories investigated (ranging from carotid to peripheral
arteries). e subgroups are not well dened in terms of
accuracy of the method in dierent body regions. Most notably, it would have been desirable to have separate results for
the calf arteries, as this is the only peripheral vascular territory for which a supplementary CEUS examination appears
to have some justication. Using the ultrasound strategy presented above, an ultrasound contrast agent is only necessary
in those cases where the standard technique fails to unequivocally identify a suitable target vessel for a planned bypass
onto a calf artery. is is typically the case in long-standing
diabetes mellitus with medial sclerosis, where acoustic shadowing obscures long vessel segments. However, medial sclerosis impairs CEUS evaluation as well. Overall, therefore, the
use of microbubble contrast agents in patients with PAOD
has not met initial expectations. In the clinical setting, CEUS
is used only in very specic circumstances. e high resolution aorded by state-of-the-art ultrasound equipment
allows reliable evaluation of most patients using standard
color duplex imaging. And in those instances where evaluation is degraded by artifacts, the problem is rarely overcome
even when using CEUS.
2.1.6.1.12 Identication ofPedal Target Artery
forBypass Grafting
Duplex ultrasound is an excellent supplement to angiography in identifying a suitable pedal artery or segment for distal bypass graing. e arteries below the knee can be
examined with a high-frequency transducer (10MHz), providing excellent spatial resolution and making ultrasound
superior to angiography in searching for a patent bypass target in this vascular territory. Poor opacication of calf and
pedal arteries oen limits angiographic evaluation in patients
with proximal occlusion (. Fig. 2.71 (Atlas)). A potential
bypass target artery is evaluated for plaques in the B-mode,
and a spectral Doppler tracing is obtained to establish
patency of the pedal arch (Hofmann etal. 2004). Only a few
studies have investigated the role of duplex imaging in diabetics with primary peripheral occlusion or diabetic foot
syndrome (Boström etal. 2002; Dyet et al. 2000; Schneider
and Ogawa 1998). e results are dicult to compare because
the patient populations investigated are very heterogeneous
in terms of clinical stage and severity of macroangiopathy.
What is noteworthy about these studies is that in a large proportion of patients, results for the calf arteries were inconclusive (29%), the calf arteries were not examined systematically
(22%), or ultrasound failed to visualize these arteries (13%).
e bular artery, oen the only patent calf artery in diabetics, was found to be the most dicult to evaluate by ultrasound.
Detection of an isolated stenosis in the plantar arch
remains a problem because continuous evaluation of these
arteries is not always possible. is is why duplex imaging
alone cannot be used to decide whether the posterior tibial
artery or the dorsalis pedis artery is more suitable to receive
the bypass gra. e hope of overcoming these limitations by
contrast-enhanced ultrasound (CEUS) has not been fullled.
Ultrasound microbubbles produce excessive enhancement of
collaterals (blooming eect), leading to poorer identication
of the main calf arteries (Dyet etal. 2000; Ubbink etal. 2002).
2.1.6.1.13 Multilevel Obstruction
e direct stenosis criteria discussed above apply when a
single stenosis or occlusion is present but may lead to misinterpretation in patients with multilevel steno-occlusive disease. e hemodynamic situation around a second, more
distal stenosis is inuenced by the ow eects of the upstream
stenosis. e pressure drop across the more proximal stenosis results in a lower peak systolic velocity (PSV) upstream of
the second stenosis, and the intrastenotic PSV in the second
stenosis is lower than in an isolated stenosis causing the same
degree of luminal narrowing (. Fig.2.24c). Hence, the PSV
of 180cm/s proposed as a cuto for 50% stenosis in case of
isolated stenosis will underestimate the distal stenosis in
patients with multiple steno-occlusive lesions.
For this reason, the only reliable way to grade the more
distal stenosis in these patients is to use the PSV ratio (e.g.,
doubling of PSV) rather than absolute PSV (
Study results conrm that the lower PSV at the site of more
distal stenosis in limbs with multilevel steno-occlusive dis-
ease
markedly reduces the sensitivity of duplex ultrasound
using the criterion of absolute PSV (Bergamini etal. 1995),
while other studies show the detection and grading accuracy
to be the same for sequential and isolated stenoses when the
PSV ratio is used (Sensier etal. 1996; Aly etal. 1998).
However, as noted above, stenosis grading based on the
PSV ratio becomes rather unreliable for stenoses located at
arterial origins, where the prestenotic segment has a dierent
diameter and dierent hemodynamics.
Finally, the examiner must bear in mind that, in patients
with multilevel obstruction, the poststenotic Doppler spectrum is also inuenced by distal runo. For instance, the
waveform will be more pulsatile if there is high resistance
due to severe obstruction distal to the sampling site
. Fig.2.24a, b).
(
2.1.6.1.14 Arterial Occlusion
An occlusion is characterized by the absence of ow signals
in color ow and spectral Doppler imaging. Note, however,
that absence of ow signals may also be due to inadequate
instrument settings (gain, PRF) or acoustic shadowing
caused by calcied plaque (. Table 2.10). e problem of
posterior acoustic shadowing due to calcications in the vessel wall is mainly encountered in diabetic patients with
medial sclerosis and can be overcome by comparing spectral
Doppler ndings upstream and downstream of the calcied
segment (monophasic prole downstream of occlusion) and
searching for collaterals arising upstream of the obstruction
and re-entering the main artery downstream (. Fig.2.25).
Duplex ultrasound allows highly accurate determination
of occlusion length (. Fig. 2.25e). A study of our group
. Table 2.7).
86
CF
PF
Chapter 2 · Extremity Arteries
ACFA
APFA
2
SFA
ColCol
PA PA
SFA
Col
21
a
c
. Fig. 2.24 a Diagrams illustrating the eects of peripheral outow on popliteal artery spectral Doppler tracings in supercial femoral artery
occlusion bridged by collaterals. When outow is poor due to occlusion of a calf artery (right), higher outow resistance leads to a more pulsatile
postocclusive waveform; when the calf arteries are patent, peripheral widening leads to a monophasic waveform (left) (CFA, common femoral
artery; PFA, profunda femoris artery; SFA, supercial femoral artery; PA, popliteal artery; Col, collaterals). b Illustration of the eects of dierences in peripheral outow on spectral Doppler ndings in the popliteal artery in two patients with supercial femoral artery occlusion and
comparable collateralization. b1 In the rst case, the calf arteries are patent and there is good peripheral outow. There is an acceleration time of
172ms, a peak systolic velocity (PSV) of 39cm/s, and an end-diastolic velocity (EDV) of 8cm/s (corresponding to left drawing in a). b2 In the second case, all three calf arteries are occluded, and the foot is supplied through collaterals. Here, a knocking waveform (thump pattern) is obtained
from the popliteal artery. In this case, acceleration time is 145ms with a PSV of 18cm/s. Flow is more pulsatile due to higher outow resistance
(corresponding to right drawing in a). c Anterior tibial artery stenosis in a patient with supercial femoral artery occlusion. The Doppler waveform
(from left to right) shows a typical postocclusive pattern in the prestenotic segment (delayed systolic rise, monophasic ow, PSV of only 34cm/s);
therefore, absolute intrastenic PSV (200cm/s) is an unreliable criterion for grading the anterior tibial artery stenosis in this patient. The PSV ratio
of 8 (intrastenotic PSV of 207cm/s divided by prestenotic PSV of 34cm/s) corresponds to >80% stenosis
b1 b2
including 40 legs with femoropopliteal occlusion demonstrated 0.96 correlation between angiography and duplex
ultrasound. e length of the occluded segment was less than
5cm in 21%, 5–10 cm in 54%, and over 10cm in 25% of
cases. Pelvic artery occlusion (n=30) was correctly identied
by duplex ultrasound in all patients; however, due to the
poorer insonation conditions at this level, the distal extent of
the occluded segment was sometimes overestimated by several centimeters (“dead water zone”). A similar correlation
(R=0.95in 98 extremities) between sonographic and angiographic measurement of occlusion length was reported by
the authors of another study (Karasch etal. 1993).
Slow postocclusive ow may lead to overestimation of
occlusion length
, in particular when collateralization is
poor. Further downstream, sonographic evaluation may
improve again, as the ow situation in the main artery normalizes through re-supply via collaterals. In vascular regions
dicult to evaluate by conventional sonographic methods,
intravenous administration of an echo enhancer may improve
detection of owing blood (Langholz etal. 1992). In the routine clinical setting, though, contrast-enhanced ultrasound
(CEUS) is rarely used for peripheral artery examinations.
A low PRF and high gain are needed to detect the slow
ow downstream of an occlusion and to correctly identify the
distal end of the occluded segment.
An occlusion, like a high-grade stenosis, inuences preocclusive and postocclusive Doppler waveforms. If no color ow
option is available, the examiner can approach the occluded
zone by sampling spectral Doppler information at both ends.
Flow signals from collaterals coursing parallel to the occluded
artery may be misinterpreted as patency shortly before the
relled segment of the main artery is actually reached, giving
rise to underestimation of the length of the occluded seg-
ment
. Collaterals entering the main artery can be identied
by an apparent sudden ow acceleration resulting from the
dierent insonation angle and above all by the change in ow
direction indicated by the Doppler signal (. Fig.2.25e). Once
a site of origin or re-entry of a collateral has been identied, a
ab
e
2.1 · Pelvic andLeg Arteries
87
2
c
. Fig. 2.25a–e Supercial femoral artery occlusion. a Exact determination of the length of an occluded segment is important for therapeutic deci-
sion making (PTA vs. bypass grafting). First, the length is estimated in the duplex mode using a low PRF to also detect slow ow (3.5cm in the example
shown). Supplementary evaluation for collaterals arising from or entering the main artery is recommended to conrm the measured length, especially
when calcied plaques cause acoustic shadowing and impair evaluation of the main artery. The image shows a dilated collateral segment (KOL) proximal to the occlusion (blue, ow away from transducer, left part of image) and another collateral segment relling the supercial femoral artery (red,
ow toward transducer, right part of image). b Detailed evaluation of collaterals: the dilated collaterals indicate the beginning and end of the occluded
segment (transducer moved to focus on the sites of origins of collaterals). The Doppler waveform from the origin of the collateral shows pulsatile ow
with a velocity of 50cm/s, indicating good inow into the collateral system (aliasing in the color ow image is due to small Doppler angle and does
not indicate stenosis in this case). c Detail showing the collateral resupplying the supercial femoral artery 3.5cm distal to the occluded segment.
Flow is toward the transducer (red) with a PSV of 30cm/s. d Doppler waveform from the supercial femoral artery segment (A.F.S.) resupplied by the
collateral (KOL) distal to the occluded segment. The postocclusive waveform shows rather high pulsatility with a small diastolic ow component and
early diastolic decrease in ow velocity (resulting from the reected pressure wave), a PSV of almost 40cm/s, and a rather steep systolic upstroke, consistent with adequate compensatory collateral circulation. The good collateral ow in this case maintains nearly normal pressure in the postocclusive
segment, which ensures adequate peripheral perfusion at rest without a need for arteriolar dilatation. The ndings (sonographic length of occlusion)
would theoretically justify an attempt at PTA (if clinically indicated), but in this case favor a conservative strategy: ultrasound indicates good collateral
circulation, while the relationship between the occluded segment and the collateral resupplying the main artery distal to the occlusion suggests that
there is a risk that the collateral may become occluded during PTA. e Dierent patient with short occlusion (OCC) of the supercial femoral artery. The
length of the occluded segment and the collateral origins (K) exactly match the angiographic ndings prior to PTA (V=femoral vein). Retrograde ow
in the collateral distal to the occlusion (displayed in blue, away from transducer) rells the supercial femoral artery. The Doppler waveform from the
distal popliteal artery (rightmost image) gives an estimate of the adequacy of collateralization (PSV, pulsatility)
d
88
ab
cd
Chapter 2 · Extremity Arteries
2
. Fig. 2.26 a, b Occlusion of the anterior tibial artery (v in a) in a patient with a long history of diabetes mellitus. The Doppler waveform
obtained directly upstream of the origin of the last strong collateral arising proximal to the occluded segment shows triphasic flow (compare
waveform obtained with sample volume placed in the occluded segment (b)). d The MR angiogram provides an overview of the occlusions
below the knee for documentation. The upper arrow indicates the proximal end of the occluded anterior tibial artery segment, the lower
arrow indicates refilling of the posterior tibial artery at the ankle level (compare detail resolution of ultrasound with clear visualization of
collaterals and of the plaque causing luminal narrowing). The anterior tibial artery is occluded down to the ankle level. c Occlusion of the
posterior tibial artery (a.t.p) with refilling above the ankle level by a strong collateral (kol) (arrow). The Doppler waveform from this segment
shows monophasic flow. This indirect criterion suggests upstream occlusion, which can then be confirmed by direct sonographic evaluation
of the proximal segment
Doppler waveform obtained with angle correction will identify stenosis obstructing collateral ow. Spectral Doppler
characterization of postocclusive ow is also important for
resolution transducer is used and settings are adjusted. In these
cases, spectral Doppler interrogation with high gain and a low
PRF can oen detect any residual ow that may still be present.
therapeutic decision making (medical treatment or repair).
For correct interpretation and localization of steno-
occlusive lesions below the knee (
. Fig.2.26), it is crucial to
identify the courses of the main arteries by following them
downward in their sonoanatomic locations (7 Sect. 2.1.6.1.4).
In addition, the accompanying veins can be used as landmarks.
is is important in order not to mistake an enlarged branch
that has been recruited as a collateral for the (occluded) main
artery. Ultrasound identication of segmental occlusion in this
territory may be seriously degraded by medial sclerosis with
acoustic shadowing in patients with a long history of diabetes
mellitus. In such cases, indirect evidence of occlusion may be
obtained by comparing proximal and distal waveforms.
e ow rate downstream of multilevel occlusions with
poor collateralization may occasionally drop below the limit of
detection of (color) duplex imaging – even when a high-
2.1.6.2 Arterial Embolism
Arterial embolism with ischemia is typically of cardiac origin
(80–90%). e remaining cases are accounted for by arterioarterial emboli, chiey arising from a partially thrombosed
aneurysm and rarely from an atherosclerotic lesion.
e site and length of occlusion are identied by the
absence of ow signals in spectral Doppler or color duplex
ultrasound. In the less common case of subtotal embolic
occlusion, some residual ow will be detected along the
hypoechoic thromboembolus near the wall (see . Figs.2.84
and 2.85 (both Atlas)). An embolic occlusion is suggested by
the demonstration of a hypoechoic and homogeneous
mass
in the vessel lumen, good delineation of the wall with
preservation of its smooth contour, and the absence of
plaques.
2.1 · Pelvic andLeg Arteries
89
2
Embolic occlusions typically occur at bifurcations, where
the embolus creates a nidus for the formation of appositional
thrombi that may extend proximally to the site of the nearest
hemodynamically signicant branching. Flow proximal to an
occlusion is known as stump ow, which is very pulsatile
with a markedly reduced peak systolic velocity (PSV), giving
rise to a knocking waveform. Any residual ow along a
thrombus is typically also relatively slow. A hemodynamic
pattern similar to that caused by stenosis, with high PSV, may
be seen when the thrombus is short. e distal end of the
occlusion is identied using a low PRF and high gain in order
not to miss the slow ow in the postembolic segment (due to
poor collateralization). In addition to identifying and characterizing the embolic occlusion, searching for the source of
the embolus
tion (echocardiography, duplex ultrasound of the aorta and
peripheral arteries). In the peripheral arteries, the search
should focus on a possible popliteal artery aneurysm.
2.1.6.3 Aneurysm
2.1.6.3.1 True Aneurysm
An aneurysm is an abnormal, local dilatation of an artery to
at least twice its normal diameter. e most commonly
aected arteries are the abdominal aorta and the popliteal
artery. Popliteal aneurysms account for 85% of all peripheral
artery aneurysms and are found in up to 1% of men aged 65
to 80 (Trickett etal. 2002). ey are bilateral in 53% of cases,
and 14% of patients have a concomitant aortic aneurysm
(Diwan etal. 2000). Peripheral aneurysms of the femoral and
iliac arteries are predominantly seen in patients with dilated
angiopathy (Schuler etal. 1993). An aneurysm is identied
on transverse gray-scale images as a saccular or spindleshaped dilatation
aneurysm are oen apparent through their slightly higher
echogenicity relative to owing blood and are conrmed by
the absence of color ow. rombotic deposits can cause
stenosis, in particular when they occur at the distal end of an
aneurysm. Absence of ow signals suggests a completely
thrombosed aneurysm. Angiography is not the method of
reference for assessing a partially thrombosed aneurysm
while computed tomography (CT) depicts the morphology
and extent of an aneurysm but provides no hemodynamic
information. Patients with an isolated occlusion in the popliteal territory should undergo an ultrasound examination to
rule out a thrombosed aneurysm or vascular compression
syndrome prior to a radiologic intervention.
Popliteal artery aneurysms can occlude or rupture. A
popliteal aneurysm containing thrombotic deposits can
cause embolic occlusion of peripheral vessels, which in the
worst case may lead to limb amputation.
Surgery is indicated when the diameter of the aneurysm
exceeds 2 cm (Robinson and Belkin 2009; Michaels and
Galland 1993) and also for smaller ones when they are saccular or contain thrombotic deposits (. Fig. 2.27). is is
because thrombotic aneurysms in the knee area are exposed
to greater shear stress when the knee is bent and therefore
(. Fig.2.27) is an integral part of the examina-
of the vessel lumen. Mural thrombi in the
have a higher risk of embolism even when they are small.
While, in general, popliteal artery aneurysms <2 cm are
managed conservatively and monitored, 18–35% become
symptomatic and may require surgery even before they reach
a size of 2cm.
Overall, in patients with popliteal artery aneurysm, the
risk of rupture is less relevant than the risk of peripheral
embolism arising from thrombus, and diameter is not the
main criterion in identifying candidates for surgical repair.
Detection of
task in these patients. Even a small popliteal artery aneurysm
should be operated on if partial mural thrombosis is demonstrated (. Fig.2.27c, d).
Duplex ultrasound is the method of choice, yielding
reliable information on the diameter of the aneurysm, its
shape, and the presence of thrombosis (see . Figs. 2.87
(Atlas) and 2.27). is information allows identication of
surgical candidates and planning the surgical procedure. An
aneurysm is supercial and can be examined with a highresolution transducer. e diameter is measured, and thrombotic material in the lumen is identied (absence of color
ow) in transverse orientation, while the shape is assessed in
the longitudinal plane.
2.1.6.3.2 Pseudoaneurysm
A pseudoaneurysm (also known as false aneurysm) is an
encapsulated extravascular collection of blood that communicates with the feeding artery through a hole in the arterial wall.
It is a typical complication of arterial puncture performed for
diagnostic angiography or interventional procedures and is
observed in up to 6% of individuals undergoing percutaneous
transluminal angioplasty (PTA) or cardiac catheterization.
e incidence of this complication depends on various factors,
including the diameter of the catheter and introducer sheath
used, periprocedural anticoagulation, obesity, puncturerelated problems, and inadequate compression (Hust and
Schuler 1992; Moll etal. 1991; Corriere and Guzman 2005). A
suture aneurysm is a pseudoaneurysm developing aer vascular surgery, in particular aer bypass operations. Other operations near the poplitel artery such as arthroscopic meniscal
surgery can also damage the arterial wall and thus give rise to
a pseudoaneurysm (Schäberle etal. 1995).
Pseudoaneurysms must be dierentiated from perivascular hematoma with transmitted pulsation (see
(Atlas)), but this is dicult on clinical grounds (omas etal.
1989). With duplex ultrasound, a pseudoaneurysm can be
dierentiated from hypoechoic, perivascular structures such
as hematoma, seroma, or lymphocele by the demonstration
of the characteristic to-and-fro ow pattern (. Fig.2.28a, b).
is nding is pathognomonic and requires no angiographic
conrmation. To-and-fro ow occurs in the neck of a pseudoaneurysm due to changing pressures: intraluminal pressure is high during systole, and blood ows through the
narrow neck into the aneurysm at a rather high velocity.
Under the reversed pressure conditions during diastole, the
blood ows back into the feeding artery at a slightly lower
ow rate. Reux is typically turbulent.
mural thrombus is thus the primary diagnostic
. Fig. 2.79
90
Chapter 2 · Extremity Arteries
2
a1
b
a2
c d
. Fig. 2.27 a Serial ultrasound of small popliteal artery aneurysm. a1 Small, partially thrombosed aneurysm of the popliteal artery with a maxi-
mum diameter of 13mm. When thrombus is present, even a small aneurysm like this can cause embolism with occlusion of a lower leg artery (due
to shear stress and kinking of the artery when the knee is bent). For this reason, surgical repair is indicated. Color duplex imaging with a low PRF
allows good delineation of the patent lumen in transverse and longitudinal planes. Calipers indicate the total luminal diameter. a2 Same popliteal
artery aneurysm 6months later (patient refused surgery). There is a slight increase in aneurysmal diameter to 15mm, and complete thrombosis
of the aneurysm (A. POP. AN) and trifurcation has occurred. The longitudinal image (left) shows the transition from the normal arterial lumen to
the aneurysm. b Large popliteal artery aneurysm (diameter of 3.4cm). The aneurysm is thrombosed except for the width of the normal popliteal
artery lumen (A.POP AN). This aneurysm would escape angiographic detection. The aneurysm compresses and displaces the popliteal vein (V).
There is a clear indication for surgical repair in this case. c, d Small popliteal artery aneurysm (maximum diameter of 13mm), again with partial
thrombosis except for the width of the normal arterial lumen, shown in transverse and longitudinal orientation (c). The aneurysm is the cause of
embolic occlusion of the tibiobular trunk in this patient (d). More proximally, the origin of the anterior tibial artery is patent (not shown)
Peripheral pseudoaneurysms have traditionally been treated
surgically. An alternative treatment is ultrasound- guided compression of the neck to induce clotting of the aneurysm. is
alternative option has become possible because ultrasound
enables very precise localization of the aneurysm neck relative to the skin surface (Fellmeth etal. 1991; Hustetal.1993).
a
c
2.1 · Pelvic andLeg Arteries
AS
91
2
CFA
Systole
SFA
PFA
AS
CFA
Diastole
SFA
PFA
b
AS
CFA
SFA
PFA
IIa
CFA
IIb
SFA
PFA
SFA
CFA
PFA
III
CFA
SFA
PFA
d
. Fig. 2.28a–d Pseudoaneurysm or false aneurysm. a Diagrams illustrating blood ow in the neck of a pseudoaneurysm. The alternating ow
directions result from blood entering the aneurysm sac (AS) during systole and owing back into the feeding artery during diastole (CFA, common
femoral artery; SFA, supercial femoral artery; PFA, profunda femoris artery). b Pseudoaneurysm measuring 22×11mm. The left image shows
blood ow during systole (sample volume in the neck). Blood ow is toward the transducer (red). In addition, there is aliasing. The right image (longitudinal view) shows the situation during diastole (aneurysm neck indicated by arrowheads). Flow is away from the transducer (blue). The spectral
waveform from the aneurysm neck shows high-frequency inow of blood during systole (2.5m/s) and pandiastolic ow (D) from the aneurysm sac
(below the baseline, away from transducer). (A.F.C. = common femoral artery; A.F.S. = supercial femoral artery; A.P.F=profunda femoris artery;
V=femoral vein; H=hematoma). c Illustration of ultrasound-guided compression of the aneurysm neck (IIa) and ultrasound-guided thrombin
injection (IIb). These two ultrasound-based techniques have now largely replaced surgical repair, which has become the exception. Pressure is
applied with the transducer under real-time monitoring until complete or nearly complete hemostasis has occurred (indicated by absence or near
absence of ow signals), which may take 10–45min. If residual ow persists in the aneurysm, a compression bandage will usually lead to complete thrombosis by the next day. For thrombin injection treatment (IIb), a needle is advanced into the lateral third of the aneurysm for dropwise
thrombin injection (5000IU in 2–5mL saline solution), both under ultrasound guidance. Fast injection and needle placement near the neck must
be avoided to minimize the risk of thrombin spilling into the arterial circulation. d Treatment of pseudoaneurysm by thrombin injection. The color
duplex image (left) depicts ow in a pseudoaneurysm arising from the femoral artery (A.F.). The aneurysm is surrounded by hematoma (H) (sample
volume in aneurysm neck). The next image shows nearly complete thrombosis of the aneurysm after injection of 2000IU thrombin (in 2mL saline
solution) following ultrasound-guided insertion of the needle (bright echo in the left portion of the aneurysm, indicated by arrow). The nal image
(right) shows the situation after repositioning of the needle (N) and injection of a second, small amount of thrombin: complete hemostasis of the
aneurysm is indicated by the cessation of color ow within the sac. Patent femoral artery (A.F.) and vein (V) posterior to the aneurysm
rombosis occurs aer 10–30min of compression with the
transducer (see . Fig.2.94 (Atlas)).
Published studies on ultrasound-guided compression
. Table 2.11 Ultrasound-guided diagnostic and therapeutic
vascular interventions
treatment of pseudoaneurysm (Krumme etal. 1995; Lange
etal. 2001) report success rates of 66–86% aer compression
for an average of 30–44min (Coley etal. 1995) and a recurrence rate of 4%. Compression treatment fails in most
patients on anticoagulation treatment. In contrast,
ultrasound- guided thrombin injection for induction of
thrombosis has success rates of 93–100% (3% recurrence
rate) and is also successful in most patients on anticoagula-
Pathology Interventional treatment/measure
Pseudoaneurysm
(typically iatrogenic)
Postoperative uid
collection around
grafts
Compression of aneurysm neck
Thrombin injection
Ultrasound-guided puncture for
diagnosis and possibly treatment:
infection, abscess, seroma, lymphocele,
graft reaction?
tion treatment (. Table 2.11; Vicente and Kazmers 1999;
92
Chapter 2 · Extremity Arteries
Wixon etal. 2000; Corriere and Guzman 2005). rombin
treatment of pseudoaneuryms has a complication rate of up
to 4%. e most dreaded complication is severe limb isch-
2
emia due to distal thrombin migration (up to 2%), which
may even result in amputation of the aected limb.
Inadvertent occlusion of a distal artery during thrombin
treatment requires immediate heparin administration and
prompt initiation of intra-arterial thrombolytic treatment.
e risk of thrombin migration can be minimized by a
meticulous technique with slow instillation of the highly
concentrated thrombin solution (e.g., 5000IU in 5mL) starting in the periphery of the aneurysm sac.
Sonographically, the neck of a pseudoaneurysm is identied by spectral Doppler interrogation, which will demonstrate
forward and reverse ow components as blood enters the
aneurysm during systole and exits during diastole. is to-
. Table 2.12 Duplex ultrasound in nonatherosclerotic
vascular disease
Ultrasound
technique
B-scan (morphol-
ogy)
Doppler
(hemodynamics)
Structures that can be evaluated/
Findings
Vessel lumen (thrombotic deposits)
Vessel wall (cysts, concentric inammatory wall thickening; dierential diagnosis:
plaques)
Perivascular structures (external
compression)
Stenosis (hemodynamic signicance of
narrowing caused by perivascular or
mural structures)
Functional test (plantar exion: increase in
stenosis severity)
Occlusion (collaterals)
and-fro ow pattern causes a characteristic audible Doppler
signal (steam engine sound). Although ultrasound is impaired
by hematoma and scattering due to edema, the needle for
thrombin instillation can be reliably placed because it is easily
recognized by its high echogenicity within the hypoechoic or
anechoic pseudoaneurysm. Rapidly moving the needle tip
back and forth will help inlocating the needle and checking for
5 Vessel wall tumor
5 Vascular compression syndrome (entrapment syn-
drome)
5 Adventitial cystic disease
correct positioning. Injection results in instantaneous thrombosis around the needle tip and, if the solution is injected
slowly, will prevent escape of thrombin into the bloodstream.
Spilling into distal arteries can occur only if the needle is mistakenly placed in the neck or if thrombin is injected as a bolus.
Case reports exist of thromboembolic complications with
severe limb ischemia nally resulting in amputation. Some
authors therefore recommend starting injection near the wall;
however, areas near the neck will thrombose spontaneously
once the aneurysmal sac has been obliterated.
rombin injection has the advantage of rapidly inducing
hemostasis, while compression therapy is less expensive and
has the added benet of reducing the aneurysm volume,
leaving a smaller hematoma that produces less swelling and
pressure (
. Fig. 2.28c). In patients on anticoagulation or
clopidogrel therapy, hemostasis can be induced by thrombin
injection but not by compression treatment. e only pseudoaneurysms dicult to treat by thrombin injection are
those with a large defect in the feeding artery and aneurysms
with very turbulent, circulatory blood ow in the sac (see
. Figs.2.81 and 2.79 (Atlas)), which washes away the throm-
bin before a clot begins to form at the needle tip.
Antiography or venography (the traditional gold standards)
may be limited in identifying the cause of vascular compression (see . Figs. 2.91, 2.92, 2.93, 2.94, and 2.95 (all Atlas)),
especially when occlusion has already occurred.
(Color) duplex imaging provides information on the
degree and hemodynamic relevance of luminal narrowing
and enables evaluation of the vessel wall and perivascular
structures, thus allowing identication of the underlying
cause in patients with nonatherosclerotic vascular disease
(. Table2.12).
Suspected compression of an artery by muscular structures (entrapment syndrome) can be conrmed by functional
tests, and its hemodynamic signicance can be determined
by spectral Doppler (see . Figs.2.31, 2.94 (Atlas), and 2.95
(Atlas)). In addition, duplex imaging can identify vascular
complications of compression such as development of mural
thrombosis or postocclusive aneurysm and occlusion.
Many nonatherosclerotic conditions predominantly
aect the popliteal artery
, owing to its close proximity to
the joint and muscles in the popliteal fossa. Duplex ultrasound should be the rst-line modality to search for the
underlying cause and initiate proper therapeutic manage-
2.1.6.4 Rare Stenosing Arterial Diseases
ofNonatherosclerotic Origin
e popliteal artery is a common site not only of atherosclerotic stenosis and occlusion or embolism but also of rare vascular disorders, in particular compression syndromes.
Nonatherosclerotic vascular conditions include:
5 Embolism
5 Aneurysm
5 Intimal dissection
5 Arteritis
ment in patients with isolated popliteal artery occlusion
(angiography or magnetic resonance angiography). One possible cause is complete thrombosis of an aneurysm. e popliteal artery is the second most common site of aneurysm
aer the aorta. In a study of 1190 patients with stage II–IV
PAOD according to Fontaine, angiography demonstrated
isolated popliteal artery occlusion in 51 patients.
e subsequent ultrasound examination of these popliteal occlusions identied atherosclerotic changes with severe
plaque as the cause of occlusion in 47% of cases. Embolic
occlusion was sonographically diagnosed in 21.5% and was