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31 Angioplasty andStenting oftheMesenteric Arteries
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Fig. 31.4 Access site for retrograde open mesenteric artery stenting.
After thromboendarterectomy and venous patch angioplasty of the
SMA, retrograde patch puncture allows artery cathterterization and
insertion of a 7Fr long sheath
329
debris in the lter, but failed to prevent distal emboly in 6%
of patients. Embolic protection devices are not currently
recommended.
Stent aring is widely use in visceral arteries endovascular repair. The rst argument is that proximal aring makes
secondary reintervention easier by facilitating stent catheterization. Secondly, in a retrospective study of 150 patients
treated for chronic mesenteric ischemia by CA or SMA
stenting, ostial aring was observed as the single factor on
multivariate analysis associated with higher patency [28].
But this study was conducted with balloon expandable bare
stents.
Specic Revascularization oftheInferior
Mesenteric Artery
xenologous pericardium patches. The sheath is then introduced after patch puncture (Fig.31.4). Long sheath allows a
longer distance between the operator and the C-arm providing a better radiations protection.
Type ofStent
Balloon expandable stents are the rst choice to treat
proximal stenosis/occlusion due to highest radial force.
The use of covered balloon expandable stents is based on
the principle of lowering the intraoperative embolic risk
and long-term myointimal hyperplasia stenosis [22].
Covered stents have already proved their benet in other
anatomical localization such as the iliac arteries [23, 24],
supercial femoral arteries. In a large monocentric prospective study from an intestinal dedicated stroke center,
covered stenting is associated with a primary and a secondary patency rate of 83% and 99% respectively. Other
study has shown a decrease of 40% of restenosis and an
increase of 28% of freedom from symptoms recurrence
compared to bare stents [25]. Based on non- randomized
or retrospective studies, the American guidelines recommend the use of covered stents in CA and SMA stenting
[8]. Results of a multicentric randomized control trial will
probably conrm the signicant benet of covered stents
in mesenteric arteries stenting [26]. Finally, the most
commonly used size of stent in the SMA is 7mm×32mm
in our experience [18].
Other Technical Considerations
The use of endovascular embolic protection devices has
been described for treatment of sever calcied lesions or
associated with thrombus [27]. It appears to be feasible and
safe with a third of the patients presenting macroscopic
Percutaneous angioplasty, of the inferior mesenteric artery
(IMA) can be considered in selective cases when revascularization of the CA and SAM is not feasible [29]. Usually,
IMA has a minor bowel feeding territory. In case of chronic
occlusion of CA and SMA, the IMA car be hypertrophic due
to ow increase, but regarding this artery diameter, angioplasty is mostly performed without stenting.
Anticipated Complications
Stenting of mesenteric arteries provides a signicant reduction of perioperative complications rate compared to open
surgery with a similar long-term survival [8]. Nevertheless,
intraoperative complications are described.
Complications of mesenteric arteries stenting include distal embolization (4%), branch perforation and hematoma
(2%), distal dissection (1%), stent dislodgment (1%), and
stent thrombosis (1%) [30]. Distal embolization might be
reduced by the use of embolic protection devices but the few
studies using those devices failed to prove the benet of the
technique [27]. Branch perforation should be prevented by
checking the distal position of the guidewire and an anteroposterior completion angiography should be performed at
the end of the procedure to track that kind of complication.
Distal artery dissection is probably underestimated in SMA
stenting and is favorized by stent oversizing or recanalization. Treatment consists of stenting prolongment using a 6 or
7mm auto-expandable bare stent landed more distally. First
collaterals can be covered with the bare stent if needed to
treat extensive dissection. Stent dislodgment is a very rare
complication favored by stent undersizing, major stent overhang in the aorta. In our experience, dislodgment can be
observed in ROMS procedure while movements of the sheath
can provide stent shifting [18]. And nally, stent thrombosis
can occur after distal dissection or major recoil after stent
placement, especially in case of severely calcied stenosis. It
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A. Girault et al.
appears also to be one of risk factor of delayed occlusion.
Recoil has to be tracked on the completion angiography
which should be performed on the lateral view but also in the
antero-posterior view. Prevention consists in the placement
of a second stent or the use of high-pressure balloon.
Perioperative Care andFollow Up
Former prognosis of AMI was very dark with a postoperative mortality of 50–80% in previous studies [1].
Organization of intestinal stroke centers and standardization of the medical treatment change the prognosis of AMI
with a dramatically decrease of postoperative mortality
around 20% [4]. All patients presenting AMI should receive
a multimodal medical support including curative unfractionated heparin treatment, anti-platelet therapy, hemodynamic management, oral antibiotics for bowel
decontamination, bowel rest, parenteral nutrition and proton pump inhibitors (Table31.2) [4]. In case of early-stage
AMI, emergent revascularization should be performed by
endovascular techniques avoiding laparotomy. In late presentation, revascularization leads to necrosis delimitation
and abdominal exploration and eventual bowel resection
are mandatory. Initial follow-up is performed in intensive
care unit and “second-look” laparotomy can be discussed
depending of patient evolution or initial bowel aspect.
Chronic mesenteric ischemia treated with angioplasty and
stent of the SMA had dual antithrombotic treatment for
3–6 months, also depending of the type of stent used.
Discharge from the hospital occurs usually the day after the
operating day depending on the general and the nutritional
status. Clinical follow-up remains essential during the rst
year after mesenteric artery revascularization, especially
stenting, considering the regularity of symptoms recurrence
due to in-stent restenosis and the potentially severe consequences of stent occlusion. In a prospective study of 145
Table 31.2 Multimodal treatment of arterial acute mesenteric ischemia [4]
Medical therapies:
– Curative unfractionated heparin treatment
– Anti-platelet therapy
– hemodynamic management
– Oral antibiotics for bowel decontamination
– Bowel rest
– Proton pump inhibitors
Emergent bowel revascularization rst
Bowel resection if needed
patients with a mean follow-up of 12months, recurrence of
symptoms occurred in 17% and in-stent restenosis was
observed in 39% on routine DUS imaging. Currently, no recommendation exist on the follow-up strategies [7]. But
European vascular surgery guidelines consider a repeat follow- up by clinical assessment and a long-term imaging follow- up [3].
Case Presentation
Continued from page 331
Under local anesthesia and sedation. Ultrasound-guided
left femoral access was obtained. A standard 6 Fr sheath was
placed and a dose of 50 UI/kg of heparin sodium was administrated. A 7 Fr long steerable sheath (7 Fr Tourguide,
Medtronic) is introduced over a semi-stiff long guidewire.
Antegrade recanalization of the SMA is initiated with a
0.035″ angled standard hydrophilic guidewire (Radiofocus,
Terumo) and a BER catheter. Intraluminal recanalization has
to be preferred to subintimal one. In case of failure, different
types of crossing catheters can be used. But our preferred
technique for occlusion, is the use of the distal end of the
guidewire allowing to have enough push to cross the heavy
occlusion (Fig. 31.5, left panel). The BER catheter is
advanced through the wire and intraluminal position of catheter’s end is checked by blood backow and by an angiography through the catheter. The distal SMA is catheterized and
wire is exchanged for a 0.035″ Rosen wire. Predilatation of
the occlusion is performed using an undersized
4mm×20mm to minimize the risk of distal artery dissection (Fig. 31.5, right panel). The lesion is stented using a
7mm× 32 mm balloon expandable covered stent (Atrium
V12, Getinge). Control angiogram showed a small recoil on
the recanalization site and a small image of dissection at the
distal of the stent. Both problems were solved using a
7mm×40mm autoexpandable nitinol stent (Absolut pro,
Abbott) landed 15mm more distally in the SMA (Fig.31.6,
left panel). Final angiography conrmed the patency of the
recanalization with no distal complications (Fig.31.6, middle panel). Abdominal pain immediately disappeared postoperatively. Postoperative course was uneventful and
renutrition was performed progressively. Patient was discharged on fth post-operative day. Patient was treated by
dual antiplatelets therapy (Aspirin 75mg/day and Clopidogrel
75 mg/day) during 3 months and then Clopidogrel was
stopped. General status improved and body weight increased
of 7kg in 6 months. Follow-up CT angiography revealed a
good stent patency at 1year with no evidence of in-stent stenosis (Fig.31.6, right panel).
31 Angioplasty andStenting oftheMesenteric Arteries
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331
Fig. 31.5 Use of 7 Fr Tourguide (Medtronic) steerable sheath to allow
antegrade recanalization of the occlusion (left panel). The wire has
been exchanged for a 0.035″ Rosen wire and predilatation of the occlu-
Fig. 31.6 After proximal placement of an Advanta V12 7×32mm balloon expandable covered stent (Getinge) followed by distal placement
of an Absolut Pro 7×40mm self-expandable stent (Abbott Vascular).
Proximal covered stent was ared with an 8× 20 mm balloon (left
sion is performed using an Armada 4× 20 mm angioplasty balloon
(Abbott Vascular) (right panel)
panel). Final angiogram showing an efcient recanalization of the
SMA.Note the small recoil at the level of the heavy calcied occlusion
(middle panel). Volume rendering technique reconstruction of
12months postoperative CT angiography (right panel)
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Renal Artery Angioplasty andStent
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Insertion: AnOverview ofModern
Practice
MarkGregory andTarunSabharwal
32
Case Presentation
A 62-year-old male under the care of the renal team presents
with a rapid decline in his renal function. He has a history of
left nephrectomy 8years ago for renal cell carcinoma. The
patient also has type 2 diabetes and is an ex-smoker. He is
found to have hypertension, which is refractory to standard
antihypertensive treatment. Urinalysis demonstrates no proteinuria or haematuria. CT imaging obtained as follow-up
for his renal cell carcinoma has previously noted incidental
right renal artery stenosis. The Interventional Radiology
team is consulted regarding the feasibility of revascularising
the kidney.
Introduction
Balloon angioplasty of the renal artery was rst undertaken
by Andreas Gruntzig in 1978, followed a decade later by the
rst renal artery stent deployment by Palmaz and colleagues
[1]. The practice of renal artery angioplasty and stenting
steadily gained popularity over the subsequent decades
before a rapid expansion in case numbers in the early 2000s;
more than 60,000 procedures were completed in the US in
2005 [2].
The publication of a series of randomised controlled trials
assessing outcomes for renal artery stenting against best
medical management alone, most notably the ASTRAL and
CORAL studies, has led to a dramatic decrease in the number of cases undertaken [3]. Although these studies have
been criticised for underrepresenting the most severe cases,
they have demonstrated that for the majority of patients with
mild/moderate renal artery stenosis, modern antihypertensive regimes offer effective management. Consequentially,
stenting of the renal artery no longer represents a routine
M. Gregory (*) · T. Sabharwal
Guy’s and St. Thomas Hospital, NHS Foundation Trust,
London, UK
e-mail: mark.gregory10@nhs.net
intervention and is reserved for a number of specic clinical
circumstances, where it remains an important treatment
option.
This chapter outlines the indications for renal artery intervention, preoperative preparation and imaging, modern
interventional techniques, complications and outcomes. The
use of renal artery stents in fenestrated endovascular aortic
repair has been covered elsewhere and is considered outside
the remit of this chapter.
Overview ofRenovascular Disease
andIndications forIntervention
Overview ofRenovascular Disease
Renovascular disease is an umbrella term encompassing a
number of aetiologies of renal artery stenosis. Atherosclerotic
renal artery stenosis (ARAS) is the most common cause and
the primary focus of this chapter. Fibromuscular dysplasia
(FMD) is a leading cause in younger (particularly female)
patients. Less common aetiologies include renal artery dissection, arterial embolus and the vasculitides.
The reduction of blood ow to a kidney, resulting from
renal artery stenosis, reduces perfusion pressures within the
kidney and activates the renin-angiotensin-aldosterone system (RAAS). This leads to systemic vasoconstriction,
sodium retention and a resultant increase in systemic blood
pressure, a phenomenon termed renovascular hypertension.
Renovascular hypertension is thought to account for around
2% of all cases of hypertension, although its prevalence
increases to around 7% in patients over 65 [3].
Often detected incidentally in asymptomatic patients,
renovascular disease can cause a spectrum of clinical conditions including ischaemic nephropathy (decline in kidney
function secondary to low perfusion pressure), renovascular
hypertension and congestive heart failure. The clinical spectrum is inuenced by factors including whether a stenosis
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2024
G. Geroulakos et al. (eds.), Mastering Endovascular Techniques, https://doi.org/10.1007/978-3-031-42735-0_32
333
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M. Gregory and T. Sabharwal
occurs acutely or develops insidiously, contralateral kidney
function and cardiac reserve [1, 2].
Clinical suspicion of renovascular disease is generally
raised in the context of hypertension that is resistant to antihypertensive medication or progressively deteriorating renal
function without an alternative cause. An abrupt onset of
symptoms may further raise suspicions, as well as known
vascular disease elsewhere in the body.
Indications forIntervention
Whilst conceptually it may seem prudent to restore renal
blood ow in all cases of renal artery stenosis, activation of
the RAAS requires a reduction in renal perfusion pressure of
around 20% and renal parenchyma can be preserved despite
reductions in pressure of up to 40% [3]. As a result, arterial
stenoses occluding less than 70% of the lumen are unlikely
to be of clinical signicance. Conversely in the setting of
critical renal artery stenosis leading to ischaemic nephropathy, a window for intervention exists after which revascularisation will have no benet due to an irreversible kidney
injury [3].
Modern antihypertensive medications, many of which target the RAAS, are generally well tolerated and have been
shown to be highly effective in managing the majority of
patients with renovascular hypertension [4]. As a result, there
is growing consensus that endovascular treatment for renovascular disease should be reserved for the following specic
clinical scenarios:
• Uncontrolled hypertension despite best medical
management
• Intolerance to antihypertensive medications, specically
deterioration in renal function due to the use of ACE
inhibitors
• Circulatory congestion including ash pulmonary oedema
• Progressive deterioration in renal function in the context
of known renovascular disease
• Solitary functioning kidney or bilateral high-grade renal
artery stenosis
Although a minority of patients undergoing endovascular
revascularisation will experience dramatic improvements in
blood pressure control or renal function [5], treatment should
be undertaken with the aim of mitigating, rather than curing,
specic factors. Examples might include slowing the progression of renal failure or facilitating control of previously
refractory hypertension with antihypertensive medication.
The timing of any endovascular intervention should also
be taken into consideration. As already discussed, intervention in cases of mild stenosis is unlikely to yield signicant
benet. Conversely, patients with deteriorating renal func-
tion and proteinuria are likely to be past the point where
revascularisation of a kidney will improve function [3]. In
patients with circulatory congestion, timing of intervention
will be guided by ndings from echocardiography and cardiology assessment. Patients in whom treatment is not indicated should be re-assessed at regular intervals as
renovascular disease can progress and intervention may be
needed in future.
Finally, the aetiology of renovascular disease will also
affect decision making. Cases of FMD should have a much
lower threshold for treatment than atherosclerotic renovascular disease, as endovascular intervention in FMD patients
carries less risk and is often preferable in young patients to
long-term medical management.
Given the narrow range of indications, varying aetiology
and the complexity involved in timing, decisions on endovascular treatment of renovascular disease should be made
within a multidisciplinary team setting. Treatment decisions
must be driven by specic clinical need rather than the degree
of arterial stenosis identied on imaging.
Imaging andPreoperative Preparation
All patients under consideration for endovascular renal
artery procedures should have up-to-date cross-sectional
imaging. Sonographic assessment of renal artery stenosis no
longer plays a signicant role in assessment. The choice
between CT Angiography and MR Angiography will vary
between institutions, although for patients with impaired
renal function, MRI is preferable as it avoids iodinated contrast. Vessel analysis software can be used to assess the
severity of renal artery stenosis and the resultant need for
intervention. Cross-sectional imaging should also be closely
scrutinised to assess for potential complicating factors, such
as aortic, iliac, or common femoral disease (with the potential to complicate access), accessory renal arteries, or other
anatomical anomalies.
Decisions regarding renal artery revascularisation should
be made within a multidisciplinary team setting, with input
from nephrologists, radiologists and the interventionalists
undertaking the procedure. Once the decision to treat has
been made the patient should ideally be seen in an
Interventional Radiology clinic. Clinic appointments allow
an opportunity to set realistic expectations regarding chances
of treatment success, as well as a chance to adequately consent the patient for the procedure, with full discussion of the
associated risks.
Consideration should be given in clinic as to whether the
patient will be able to lie at, keep still and follow breathing
instructions during the procedure, to allow for optimal digital subtraction angiography (DSA) imaging. Conscious
sedation or general anaesthesia may be required to achieve
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335
the above factors, although patients with atherosclerotic
renal artery lesions often have considerable comorbidities
and may be high-risk anaesthetic candidates. Anaesthetic
team presence will need to be arranged in advance, as well as
postoperative admission in high-risk cases.
In addition to the above, clinic appointments offer an
opportunity to review the patient’s medications, with particular attention to anticoagulant and antiplatelet medication as
well as the patient’s antihypertensive regime. Typically, antiplatelet medication should not be withheld prior to the
procedure. Indeed, some centres initiate either aspirin or
clopidogrel prior to the procedure in cases of renal artery
stenting [6]. Antihypertensive medication is usually continued on the day of the procedure, although ACE inhibitors are
generally omitted and some centres will instruct the patient
to halve their usual antihypertensive dose. If there is no
capacity to see patients in clinic, they should at least have a
nurse-led pre-assessment where medication instructions can
be given.
Renal Angioplasty andStent Insertion
Technique
Techniques for renal angioplasty and stenting continue to
evolve with advances in technology [6–9] and are outlined
below. Procedures should be performed in an angiography
suite, by appropriately trained individuals experienced in
endovascular intervention. In the United Kingdom and
Europe cases are predominantly performed by Interventional
Radiologists, whereas Interventional Cardiologists and
Vascular Surgeons undertake many such procedures in North
America.
General Technical Considerations
The majority of cases can be undertaken under local anaesthesia, either as a day-case procedure or with overnight inpatient admission. As discussed above, patients who may not
tolerate a procedure under local anaesthetic should be identied in advance, with anaesthetic support arranged.
Pre-procedure imaging can be utilised such that the level
and orientation of the target renal artery are known in
advance. The angle of the proximal renal artery with respect
to the aorta should also be conrmed. This allows DSA
imaging to be obtained at the optimal angle to demonstrate
the origin of the vessel in prole, essential for accurate stent
deployment [6, 10]. Finally, vessel analysis software can be
used to accurately calculate the normal diameter of the vessel, for accurate angioplasty and stent sizing.
The patient cohort requiring renal artery intervention has
a high rate of chronic renal insufciency. Prior consideration
should therefore be given to the use of iodinated contrast.
The successful use of CO2 angiography has been described
[11] and represents a safe option in centres experienced in its
use. In many cases, however, the total volume of iodinated
contrast can be successfully kept to a minimum, with the
omission of initial aortography (through utilisation of preprocedure imaging) and image optimisation throughout the
procedure [6]. In patients who are allergic to iodinated contrast, CO2 angiography or gadolinium represents an alternative option.
Access, Renal Artery Cannulation andEmbolic
Protection Devices
Ipsilateral common femoral artery access is suitable in the
majority of cases. Ultrasound-guided access and use of a
micro-puncture kit may reduce the incidence of access site
complications, known to be the most common complication
associated with the procedure [7, 12]. Brachial access is an
important alternative in patients with severe caudal angulation of the target renal artery, infrarenal aortic aneurysm or
highly diseased iliac arteries. The use of the brachial artery
comes with a higher rate of access site complications [13]
and requires additional technical considerations, primarily
the selection of a sheath or guide catheter long enough to
reach the renal artery ostium and the use of longer shaft
stents. Once access has been established, unfractionated heparin can be given intra-arterially, with an initial dose of
5000iU and further boluses to maintain an activated clotting
time (ACT) between 220 and 300s. In some centres heparinisation is delayed until after the renal artery has been
cannulated.
Variable guidance exists regarding the optimal choice of
sheath and catheter combination for safe access to the target
renal artery. Some texts advocate a long 6fr sheath, such as
a 40cm Flexor Balkan or 45cm Flexor Ansel Guiding Sheath
(Cook, Bloomington, Indiana) or a 45 cm Destination
Guiding Sheath (Terumo, Tokyo, Japan). Others advocate a
short 7fr sheath with the use of a 6fr guide catheter such as
a Hockey Stick Guiding Catheter or a Renal Standard Curve
Guiding Catheter (Merit Medical, Utah) [7, 14]. Both the
guide sheaths and the guide catheters are positioned at the
renal artery ostium, providing support to facilitate the crossing of tight stenoses and delivery of devices, as well as providing a port for contrast injection.
There is further variation with respect to the technique for
cannulating the target renal artery. The potential for intraprocedural embolisation of particles from atheromatous
lesions is well established, having been demonstrated in both
invivo [15, 16] and exvivo models [17]. Meticulous technique is therefore warranted to reduce the risk of embolisation during the initial crossing of the stenosis, especially in
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atherosclerotic lesions at the ostium. Older texts advocate the
use of 0.035in guidewires such as Bentson or Terumo wires,
through 4fr catheters [6]. Cannulation with hooked catheters
such as the Visceral Selective 1 catheter (Cook, Bloomington,
Indiana) has also been described with anecdotal evidence of
lower risks of dissection and embolisation [6].
There is consensus in more recent texts that the use of
0.014in guidewires to cross stenoses is likely to reduce the
risk of dissection or embolisation [10], although there are no
prospective studies conrming superiority. The ‘No Touch
Technique’ [6, 14] has also been described, which aims to
further reduce complications during renal artery cannulation.
In this technique the guide catheter or sheath is prevented
from engaging the renal artery by a 0.035 wire placed against
the aortic wall superior to the renal ostium. The wire is
retracted such that only the soft tip remains against the superior aortic wall, allowing the guide catheter or shaped sheath
to take its desired form, pointing towards the renal artery
ostium. At this point a 0.014 wire can be advanced through
the guide catheter or sheath into the renal artery and across
the stenosis [14]. The 0.035 wire can then be carefully
retracted, allowing the sheath or guide catheter to engage the
vessel.
Once the guidewire has advanced through the stenosis, it
should be positioned in the distal main renal artery or a proximal rst-order branch. Distal migration of the guidewire can
result in vessel occlusion or even perforation of the renal
capsule. A short-tipped guidewire is therefore preferential to
provide enough stability to allow catheters, angioplasty balloons and stents to track across the stenosis without needing
to advance the tip into second- or third-order branches [6].
Having established a secure position across the target stenosis, some older texts advocate the measurement of pressure gradients, especially in cases of borderline lesions. A
20mmHg systolic pressure or a 10mmHg mean gradient is
considered signicant [3]. Given the more rigorous patient
selection process undertaken in modern practice and the data
provided by pre-procedure imaging, the role of pressure gradient measurement to determine the signicance of a stenosis is now limited.
The placement of embolic protection devices (EPDs) is
often advocated prior to angioplasty or stenting, given the
established risk of atheroemboli [1, 8, 9]. A variety of EPDs
are available and can be deployed in the distal main renal
artery, generally over a 0.014 or 0.018 system. Outcomes are
likely to be device and operator dependent with an associated
learning curve. A number of single-arm observational studies have been published, reporting rates of recovered embolic
debris ranging from 65 to 80% [16, 18, 19]. The majority of
these studies report comparably strong results in terms of
stabilisation or improvement in renal function; however, the
only randomised trial involving an EPD, the Angioguard
(Cordis, Vaughan, California), found no benet of its use [4].
Renal Stent Deployment
A wide range of balloon-mounted stents are available for use
in the renal arteries (Table 32.1). The majority of modern
stent designs employ a monorail delivery system over a
0.014 or 0.018 wire and range from 4 to 7mm in diameter.
Drug-eluting stents are commercially available, and whilst
their superiority to bare-metal stents has not been proven,
they may have a role, particularly in arteries less than 4mm
in diameter [20]. Pre-dilation of a stenotic lesion up to 4mm
was advocated with earlier-generation stents but is rarely
required with modern, low-prole devices [6]. Similarly,
advancement of the sheath/guide catheter across the stenosis
for delivery of the stent, followed by retraction to the ostium
prior to deployment, was advocated historically but is not
stipulated in the instructions for use of modern designs.
Table 32.1 Suggested endovascular toolkit for renal artery angioplasty and stent insertion. These are only a few suggested options based
on the author’s experience and can cover the vast majority of cases.
Cases involving brachial access will require longer sheaths, catheters
and guidewires as well as long-shaft balloons and stents
Manufacturer Specications
Sheaths
Flexor Ansel
guiding sheath
Destination guiding
sheath
Guidewires
J-tip starter
guidewire
Hi-torque command Abbott 0.014in, 200cm
V-14 ControlWire Boston
Catheters
Angled catheters
(various)
Low-prole
catheters
IVUS
Eagle eye platinum Philips 150cm (0.014 system, 5fr
Embolic protection devices
SpiderFx Medtronic 6-7mm, 190cm (0.014
Angioplasty balloons
Coyote OTW Boston
Sterling OTW Boston
Balloon-expandable stents
Tsunami Terumo 4–7mm diameter, 15–30mm
Formula Cook 5–7mm diameter, 15–30mm
Rx Herculink Abbott 5–7mm diameter, 15–30mm
Cook 5 or 6fr, 45cm
Terumo 5 or 6fr, 45cm
Boston
scientic
scientic
Various 4 or 5fr
Various 2.6fr
scientic
scientic
0.035in, 150cm
0.014in, 180cm
sheath)
system)
4–7mm diameter, 20–40mm
length, 5fr sheath
4–7mm diameter, 20–40mm
length, 5fr sheath
length, 5fr sheath
length, 5fr sheath
length, 6fr sheath
32 Renal Artery Angioplasty andStent Insertion: AnOverview ofModern Practice
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The selection of an appropriate length and diameter stent
is achieved primarily with reference to the pre-procedure
imaging. The majority of texts stipulate that for ostial lesions
the stent should be deployed with the proximal aspect projecting 2mm into the aortic lumen and that stents should not
overexpand the natural diameter of the vessel. The use of
intravascular ultrasound (IVUS) may be considered to check
diameter and length measurements and for certainty regarding stent positioning [10]. IVUS allows excellent visualisation of the stenosis and the healthy distal vessel in which to
land the stent and can be used in conjunction with DSA
imaging of the renal artery to maximising accuracy of
deployment.
Once the correctly sized stent has been chosen and positioned across the stenosis, the position can be rechecked with
contrast injection through the sheath and small adjustments
made. Slow balloon ination combined with a steady hold on
the sheath, stent and guidewire will minimise untoward
movement during deployment. Following deployment, the
fully deated balloon should be carefully retracted through
the stent under uoroscopic guidance. Subsequent DSA
should be closely scrutinised for dissection, perforation and
for evidence of embolisation, indicated by abrupt cut-off of
distal renal vessels or segmental perfusion defects. IVUS
also offers potential benet here, identifying dissections that
may be missed on DSA and conrming a satisfactory position and expansion of the stent. In cases of suboptimal stent
expansion, post-dilation with appropriately sized angioplasty
balloons should be considered.
Technical Considerations forAngioplasty
Angioplasty of the renal artery is now predominantly
reserved for patients with FMD. In these cases, the technique
for accessing the target renal artery may be simplied, given
the signicantly reduced risk of atheroemboli. The use of
EPDs is also less likely to be required as there is substantially less risk of atheroembolism in this cohort.
Angioplasty also has a dominant role in the treatment of
transplant renal artery stenosis (TRAS), where it is generally
preferred to stent deployment, particularly as a rst-line
intervention. In cases of TRAS, access can be considered
from either the ipsilateral or contralateral common femoral
artery; interrogation of pre-procedure cross-sectional imaging will help determine the best approach.
As with cases of stent deployment, careful analysis of the
pre-procedure imaging will determine the diameter and
length of angioplasty balloon required. IVUS may also have
a role in angioplasty planning, providing more accurate
information on stenoses than DSA imaging alone. Lowprole angioplasty balloons are available, compatible with a
0.014 or 0.018 system. Care should be taken in their posi-
tioning, ination and deation to reduce the risk of vessel
dissection. As with stent deployment, post-angioplasty imaging should be carefully scrutinised to assess for
complications.
The use of stents in patients with FMD should be avoided.
The condition usually responds well to angioplasty, and the
patient cohort is much younger, predisposing them to eventual in-stent stenosis. In angioplasty cases involving atheromatous lesions or TRAS, a suboptimal result should lead to
consideration of stent deployment. Regardless of the pathology being treated, appropriately sized bare-metal and covered stents should be available in the department to treat
cases of occlusive dissection or vessel perforation.
Closure andPost-procedure Care
Rechecking of the ACT time is useful prior to removing the
sheath. As with all procedures, care should be taken in
achieving satisfactory haemostasis to prevent access site
complications. A variety of closure devices are indicated for
retrograde common femoral access, and the technique for
haemostasis should be guided by operator experience.
Patients should be monitored in recovery for puncture site
complications and for signs of renal injury, including ank
pain and haematuria.
There is consensus in the literature that an antiplatelet
regime should be undertaken following stent deployment.
The benets of single vs. dual antiplatelet therapy have not
been conclusively determined, nor has the optimal duration
of antiplatelet treatment; clopidogrel is commonly continued
for between 8 weeks and 3 months, whereas Aspirin prescription is often lifelong [1]. Renal function should be
closely monitored in the days and weeks following the procedure, as deterioration in function is a known complication
and a subset of patients will need renal replacement therapy.
Follow-up imaging should also be arranged, primarily to
monitor stent patency, allowing for early intervention in
cases of in-stent restenosis.
Complications
Renal arterial intervention carries a wide range of known
complications. Reported complication rates vary, and there
are few studies reporting on recent cohorts, treated with
modern techniques. An overall major complication rate of
7.5% was reported in Mayo Clinic data from 140 patients
between 1997 and 2000 [21], whereas data from the CORAL
study’s 495 patients indicate a 5.2% complication rate [4].
Peri-operative mortality has been found to be 2%, although
again, there is limited recent data [5]. It is also known that
complication rates vary between operators, and there is a
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learning curve for the procedure [1, 10]. For the purposes of
this discussion, complications have been split into ‘Renal’
and ‘Non-renal’ complications.
‘Renal’ Complications
Distal embolisation is thought to occur in up to 10% of cases.
Clinical effects of embolisation vary from subclinical to segmental renal infarction. The complication has been attributed
to a causative factor in the subset of patients who experience
a rise in creatinine following intervention [12]. Techniques
to minimise atheroemboli have been discussed above.
Angiographically evident distal embolisation was reported
in 1.2% of patients in the CORAL study and should be
actively sought, as early identication may allow for attempts
at catheter-directed aspiration. In many cases however
embolisation of micro-emboli will not be appreciable on
imaging.
Renal artery thrombosis is another recognised complication, often secondary to the rupture of atherosclerotic plaques
by guidewire or catheter manipulation. Adequate heparinisation is crucial in minimising thrombus formation. Again,
catheter-directed aspiration or thrombolysis could be considered in the correct clinical context.
Arterial dissection is a common complication and may
occur during initial cannulation attempts or following intervention. Highly calcied ostial plaques are particularly prone
to dissection during cannulation. Suspicion of dissection
should be raised by tactile feedback and the behaviour of the
guidewire. Early identication is crucial prior to further
instrumentation or angioplasty, which can propagate the dissection plane and risk vessel rupture. Should dissection
occur, cannulation of the true lumen is required and can be
conrmed by DSA imaging. This can be challenging and
time consuming; adequate heparinisation is vital during this
time to minimise the risk of thrombosis.
Dissection following angioplasty or stent insertion is
often identied on subsequent DSA imaging. The complication is often attributed to the use of stents or balloons that are
oversized for the vessel and is also more likely when the distal balloon or stent does not land in healthy vessel. When
identied, dissection should be treated with either prolonged
balloon angioplasty or further stent deployment, to prevent
distal propagation of the dissection ap, which risks segmental infarction or complete thrombosis. As discussed above,
IVUS can add value in cases of dissection. Vessel rupture is
a complication of dissection and requires covered stent insertion to treat, or surgery if this strategy fails.
Unscrupulous care of the guidewire can lead to perforation of the distal renal arteries and the renal capsule. This can
lead to pseudoaneurysm formation or renal/capsular bleeding. If not identied on DSA imaging, this can present with
ank pain, a deterioration in the patient’s condition, haematuria or a drop in haemoglobin. Super-selective catheter
embolisation represents the optimal rst-line treatment for
this complication and can be performed at the time of the
procedure, if identied early.
Contrast-induced nephropathy (CIN), stent migration and
restenosis are renal-intrinsic complications which tend to be
identied after the procedure. Renal function should be carefully monitored in the days and weeks following a procedure, and a standardised protocol for imaging follow-up
should be agreed upon, with access to expedited imaging if
complications are suspected. Patients at risk of CIN should
be identied prior to the procedure and steps taken to mitigate the risk. Distal stent migration is often attributed to
undersizing of stents, and modern imaging software should
help limit the incidence. Balloon-mounted stents can occasionally become displaced in transit to the target vessel and
travel systemically, often into the femoral or internal iliac
vessels. Depending on the situation it may be possible to rectify these situations with an endovascular approach using
snare devices; however a low threshold for consultation with
a vascular surgical team should be maintained.
Longer-Term Renal Complications
In-stent restenosis represents the most signicant of the
longer- term complications. Restenosis by imaging has been
found to range from 6.6 to 25% at 1year, with the wide range
likely to be due to variation in duplex and cross-sectional
assessment [5]. Modern stents report a patency rate of around
90% at 1year [22]. Target vessel revascularisation rates also
vary between studies, often given as close to 20% at 3years
[aa - 5]. Options for revascularisation include angioplasty
and stent relining.
Non-renal Complications
Access site complications account for the largest number of
reported complications (up to 20% in some studies) and
include haematoma, pseudoaneurysm and, rarely, arterialvenous stula creation [21]. Techniques to reduce access site
complications are discussed above. Thrombin injection for
the treatment of suitable pseudoaneurysms has been well
described. In cases where thrombin injection is unsuitable,
covered stents may be required for treatment.
A multitude of complications can occur secondary to the
instrumentation of the iliac vessels and aorta required for
access. Aortic or Iliac artery dissection can result in limb or
bowel ischaemia and may require further endovascular treatment. Systemic embolisation is also possible to a wide variety of locations. The likelihood of these complications
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