(arrows) successfully treated with (B) bilateral renal artery stents (arrows). The stents are positioned with appropriate overlap into

the aorta and are ballooned proximally such that they “flower” into the aorta.

MEDICAL MANAGEMENT OF RENOVASCULAR HYPERTENSION

8 Medical therapy remains the mainstay of treatment for RVH with comprehensive goals of care that

should encompass glycemic control, cholesterol reduction, smoking cessation, blood pressure reduction,

and antiplatelet therapy with aspirin for primary prevention. ACC/AHA guidelines support the use of

ACE inhibitors (ACE-I), angiotensin receptor blockers (ARBs), calcium channel blockers, and beta

blockers with a class I indication.157 While beta blockers are often utilized first line, ACE-Is and ARBs

are a mainstay of treatment for most antihypertensive regimens offering 86% to 92% efficacy.170 Renal

function monitoring is essential with the initiation of these agents as the resulting modulation of the

renin–angiotensin system with renal artery stenosis affecting a solitary functioning kidney, severe

bilateral RAS or advanced chronic kidney disease may result in acute renal failure.

SURGICAL AND ENDOVASCULAR MANAGEMENT OF RENAL

ARTERY OCCLUSIVE DISEASE

As RAS may progress with concomitant renal atrophy, renal revascularization should be considered in

select cases. Current ACC/AHA guidelines support renal revascularization for hemodynamically

significant RAS in several clinical scenarios (Table 91-2).

Arterial Reconstructive Surgery for Renal Artery Occlusive Disease

Historically open revascularization procedures represented the standard of care in the treatment of

RVH. The most common option for open renal revascularization remains aortorenal bypass with either

autogenous reversed saphenous vein or prosthetic conduit. Alternatives may include (1) nonanatomic

renal bypass based off the hepatic, splenic, or iliac arteries, (2) ex vivo renal artery reconstruction, and

(3) aortorenal endarterectomy. Nonanatomic (or extra-anatomic) renal artery bypass may benefit those

patients with medical comorbidities or aortic anatomy that prohibit aortic cross-clamping and aortorenal

bypass.176–180 The hepatic artery is used for a right-sided renal reconstruction, the splenic artery for a

left-sided reconstruction. Ex vivo renal artery reconstruction may be considered selectively for those

patients with complex, distal segmental arterial occlusive disease when balanced with the risk of

prolonged operative time, disruption of pre-existing collaterals, and the need for renal cooling.181,182

Transaortic and direct renal artery endarterectomy is particularly useful for those patients with bilateral

disease, or when arteriosclerotic renal artery occlusive disease affects multiple (i.e., accessory) renal

arteries.183–185

Table 91-2 Indications for Renal Revascularization for Hemodynamically

Significant Renal Artery Stenosis

Open surgical revascularization offers significant blood pressure and renal function improvement in

85% and 50% of patients, respectively across high-volume centers with mortality rates of 2% to

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5%.169,186–189 While to date there has been no definitive trial comparing open surgical revascularization

directly to endovascular therapy, angioplasty, and stenting appears to offer similar effectiveness with

lower morbidity and mortality. As such, endovascular measures have replaced surgery as first-line

therapy for RVH.189,190 Contemporary open surgical renal reconstructions most commonly accompany

hybrid endovascular interventions for aortic aneurysmal disease and may be considered for failed

endovascular renal revascularization.

Endovascular Renal Revascularization

Since its introduction in 1978, percutaneous renal artery angioplasty (PTA), with or without stent

placement, has virtually replaced open surgical reconstruction of arteriosclerotic renal artery stenosis.

This technique has exploded in use and for over a decade has been utilized at times perhaps

inappropriately as “prophylactic” therapy to treat clinically irrelevant renal artery stenoses.191,192 Renal

artery angioplasty alone risks arterial dissection from lesion/vessel recoil and early restenosis. Technical

success rates of PTA may be as low as 30% to 50% in patients with significant aortic “spill over” lesions.

PTA with stenting offers improved success and very reasonable long-term patency with 5-year

secondary patency rates >90%.193,194

9 Several recent clinical trials comparing renal artery stenting (RAS) to best medical management for

renal artery stenosis have failed to demonstrate a conclusive clinical benefit to the endovascular

treatment of renal artery stenosis (Table 91-3).195–199 Moreover, RAS is associated with a 1.5% to 8%

risk of major morbidity that can include infected hematoma, atheroemboli, renal failure requiring

dialysis, and lower extremity limb loss. Significant limitations apply to all of these studies, including

design flaws and selection bias.

The appropriate patient for revascularization remains elusive. Most would suggest that those patients

with refractory hypertension despite an appropriate medical regimen that includes a combination of

ACE inhibition or angiotensin receptor blockade + diuretic + amlodipine with both a hemodynamically

significant stenosis by manometric pressure gradient and overall preserved renal mass should still be

considered for therapy.200 Notably, evolving data have identified several promising predictors for

clinical improvement following renal revascularization including bilateral RAS, mean arterial pressure

>110 mm Hg, elevated baseline brain natriuretic peptide, elevated pulse pressure, and renal perfusion

as measured by “renal frame count” during angiography (defined as the number of frames required for

dye to pass through the renal parenchyma).200–204 Ongoing study remains necessary to identify

consistent indications for RAS and reliable clinical predictors of successful outcomes following renal

revascularization.

Although randomized, controlled trials assessing renal revascularization for renal artery FMD are

lacking, current guidelines support the following indications for renal revascularization in this patient

cohort: (1) resistant HTN despite an appropriate three-drug regimen, (2) HTN of short duration with the

goal being a cure of hypertension, (3) renal artery dissection, (4) RAA, and (5) preservation of renal

function in patients with severe stenosis.172,205 PTA of the renal artery is the procedure of choice for

patients with renal artery stenosis secondary to FMD offering cure rates that approach 50%, with up to

86% of patients improved following PTA, a 20% risk of reintervention, and low risk of minor

complications.172 Hemodynamic significance must be documented by manometry prior to any

intervention in these patients and success should be defined by resolution of this gradient

postangioplasty. Stenting should be utilized selectively.

Table 91-3 Contemporary Clinical Trials Comparing the Effectiveness of

Endovascular Renal Artery Revascularization to Medical Therapy

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Developmental Dysplasia

Renovascular HTN secondary to renal artery stenosis and abdominal aortic coarctation remain an

important cause of pediatric HTN, the natural history of which risks failure to thrive, heart failure,

hypertensive encephalopathy, impaired mental development, hemorrhagic stroke, and early

mortality.206 It is estimated that 5% to 10% of pediatric HTN may be explained by renovascular disease,

following thoracic aortic coarctation and parenchymal renal disease in incidence.206,207 The

pathophysiology of pediatric renovascular disease remains ill defined, as are the mechanisms by which

pediatric renovascular disease occur. FMD and neurofibromatosis type 1 (NF1) are reported as the most

common causes of pediatric renal artery stenosis in the western world.208 While the intimal FMD

variant described above is uncommon in adults, it is the most common form identified in children with

renal artery stenosis. Furthermore, histopathologic review of operative renal artery samples excised

from patient with developmental arterial stenosis reveal mainly consistent findings of intimal

hyperplasia, medial thinning, and disruption of the elastic lamina (Fig. 91-21).

Open surgical revascularization of renal artery stenosis remains the gold standard for children with

developmental lesions.206 Aortorenal reimplantation with spatulation of the renal artery and interrupted

suture lines is favored. Alternatively aortorenal bypass using hypogastric artery as conduit is favored

over autogenous venous conduit, which can dilate over time to become aneurysmal. Approximately onethird of children will demonstrate associated aortic coarctation and require concomitant patch

aortoplasty or aortoaortic bypass. The University of Michigan experience reports that benefits regarding

blood pressure control have accrued in 97% of children with this practice; specifically HTN has been

cured in 70%, improved in 27% and unchanged in 3%.206

There may be a role for angioplasty for selected cases of pediatric renal artery stenosis. Certainly this

procedure has gained substantial momentum in the past decade. The most robust U.S. experience

includes the treatment of 19 hypertensive children aged 2 to 18 years that underwent PTA for renal

artery stenosis, of which 7 patients carried the diagnosis of NF.209 While immediate technical success

was reported as 91%, only 39% of patients achieved a cure in HTN and an additional 17% of children

demonstrated improvement. In total there was a 44% rate of clinical failure and these authors conclude

that despite a high rate of technical success, PTA provides a clinical benefit in a smaller majority of

children. This is consistent with improvement or cure rates that mainly average 50% to 60% across

larger series of pediatric renal artery stenosis treated with PTA.210–212 Notably, renal PTA for the

treatment of pediatric RVH due to ostial disease may be complicated by failures requiring remedial

operations that are made more complicated by such or nephrectomy.213 Moreover, HTN cure is less

likely following remedial operation (24% in comparison to 70% as referenced above).

RENAL ARTERY ANEURYSM

RAAs are rare with an incidence of 0.1% in the general population.214–217 The natural history of RAAs

appears to be that of slow to null growth with contemporary series estimating a median annualized

growth rate of 0.06 to 0.6 mm.218–220 Aneurysm growth rate does not seem to be affected by aneurysm

morphology or calcification.219 While historic series describe rupture rates as high as 14% to 30% with

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associated mortality of 80%, contemporary rupture rates are estimated at 3% to 5% with nongestational

mortality <10%.214,217,221–224 Most ruptures are diagnosed at the time of presentation and several

authors have supported no rupture during the surveillance of nonoperative RAAs.225

Similar to other splanchnic artery aneurysms, RAAs typically present in the sixth decade with women

more commonly affected than men.214,221 Most patients will describe no symptoms, although flank pain

and hematuria are most common when symptoms do arise. Clinical examination may reveal HTN, renal

bruit or a palpable abdominal mass. Aneurysms are typically solitary, saccular, located at arterial

bifurcations, and affect the right renal artery more often than the left.225 Almost 70% of RAA may be

associated with FMD and up to 30% of patients will have an alternate arterial aneurysm.214,225,226 These

aneurysms are commonly identified as an incidental finding by axial imaging; CT is the most common

contemporary diagnostic modality, followed by magnetic resonance imaging, ultrasonography, and

catheter-based arteriography.219 Conventional preoperative arteriography is warranted given the

frequency of multiple aneurysms and arterial dysplasia affecting distal branches that may be missed on

conventional cross-sectional imaging.

Currently accepted indications for RAA intervention include size >2 cm, female gender within

childbearing age, symptoms like pain and hematuria, medically refractory HTN including that associated

with functionally important renal artery stenosis, thromboembolism, dissection and rupture. Given the

low risk of rupture, slow to null rate of growth, and improved survival following rupture some authors

have suggested that a size threshold alone of 2 cm may be antiquated and too aggressive for surgical

indication.218,219 The potential for gestational rupture remains a valid indication for repair in women of

child-bearing age as rupture during pregnancy has been described in aneurysms as small as 1 cm and

historic reports suggest maternal and fetal mortality rates that approach 92% and 100%,

respectively.227,228 Pregnancy has previously been associated with a higher rate of RAA rupture, thought

to result from increased vascular flow and hormonal changes resulting in weakening of the vessel wall

elastic tissue, no large scale studies report the true incidence.215,225 Gestational RAA ruptures occur

mainly in the third trimester with only a few case reports of rupture postdelivery.229 Notably,

contemporary outcomes for both mother and fetus may be improving, as there are recent case reports of

gestational rupture resulting in both maternal and fetal survival.

Approximately 70% of patients with RAA have HTN, with up to 100% affected in some

series.214,218,220–224,226,228 Hypotheses for the mechanism of HTN include (1) coexistent renal artery

occlusive disease, (2) distal parenchymal embolization, (3) compression or kinking of associated renal

artery branches, and (4) hemodynamic changes from turbulent blood flow within the aneurysm results

in decreased distal renal artery perfusion.214,224 Most series suggest improvement or cure in the

majority of hypertensive patients undergoing RAA reconstruction, with postoperative improvement

more likely when RVH or renal artery stenosis is identified preoperatively.221,225,228

Open surgical repair remains the gold standard for RAA management as these procedures performed

in the elective setting offer low morbidity, negligible mortality, and durable

patency.218,219,221–224,226,230,231 Options for conventional in situ reconstruction may include aneurysm

resection with (1) primary angioplastic closure with or without branch reimplantation, (2) patch

angioplasty, (3) primary reanastomosis, (4) interposition bypass, (5) aortorenal bypass, (6)

splanchnorenal bypass, and (7) plication of small aneurysms. While complex distal branch lesions were

historically treated with nephrectomy, they may rather best be approached with ex vivo repair and

autotransplantation which offers excellent technical success without major morbidity or mortality.181,232

Most recently, robotic techniques have been introduced that may become more prevalent in future

practices.233,234 Most authors advocate completion imaging before hospital discharge and long-term

follow-up with surveillance imaging.

While traditional endovascular therapies for RAA have utilized coil embolization for distal and

parenchymal aneurysms and stent graft exclusion for main renal artery lesions, the indications for

endovascular repair have broadened with the introduction of three-dimensional detachable coils,

nonadhesive liquid embolic agents (i.e., Onyx), remodeling techniques (which include balloon- and

stent-assisted coiling), and flow diverter stents (i.e., the Cardiatis multilayer stent).225,235–237 Technical

success is suggested as 73% to 100% across series with highly variable rates of morbidity (13% to 60%)

that include primarily radiographic evidence of end organ malperfusion from thromboembolism and

subsequent postembolization syndrome, negligible evidence of arterial dissections or renal compromise,

and low rates of recanalization requiring reintervention (4% to 13%).231,238–240 Although prospective

data are lacking, limited comparisons of open surgical and endovascular procedures have reported no

significant difference in mortality, perioperative morbidity, freedom from reintervention, decline in

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