renal artery stenosis (RAS); renovascular hypertension

Introduction

Etiology:

• atherosclerotic plaques*
• fibromuscular dysplasia, stenosis*
  • more common in women
  • patients under 50
• thrombosis
• embolism
• renal arterial dissection/aneurysm
• arteritis
• extrinsic compression
• occlusion by foreign body
• coarctation of aorta
• arteriovenous fistula
• post irradiation stenosis
• post transplant stenosis

* 2 most common causes

Epidemiology

• uncommon
• atherosclerotic disease: > 50 years of age
• fibromuscular dysplasia: < 30 years of age

Pathology

• the perceived reduction in renal perfusion results in release of renin & activation of the renin-angiotensin-aldosterone axis

Clinical manifestations

• epigastric, subcostal or flank bruits
• accelerated hypertension
• unilateral small kidney
• sudden development or worsening of hypertension
  • diastolic blood pressure > 120 mm Hg
• hypertension & unexplained renal failure
• hypertension refractory to 3-drug medical therapy
• impairment of renal function in response to ACE inhibitor
• extensive atherosclerosis evident in other organ systems
• flash pulmonary edema with uncontrolled hypertension
• high-grade hypertensive retinopathy
• ischemic nephropathy - glomerulonephritis
• secondary hyperaldosteronism

Laboratory

• increased serum creatinine
  • further increased after treatment with ACE inhibitor or ARB
• increased serum aldosterone

Diagnostic procedures

• plasma renin & plasma aldosterone are elevated
• renal vein renin levels
  • ratio involved/contralateral side > 1.5 suggests significant lesion
• renin activity weighted analysis point system
• screening for renovascular hypertension (sensitivity/specificity)
  • captopril test 95/95
  • captopril scan (scintigraphy) 80/100
  • renal scan 75/75
  • IVP 75/85
  • digital subtraction angiogram 90/90
  • renal vein renin 75/95

* routine testing for older adults with cardiovascular disease not recommended

Radiology

• renal angiography for fibromuscular dysplasia (gold standard & initial imaging)*
  • 'string of beads' appearance consistent with fibromuscular dysplasia
  • release of cholesterol emboli is a risk in patients with atherosclerosis
• invasive angiography remains the gold standard for confirming lesion significance prior to revascularization
• only hemodynamically significant stenoses (>=70% by imaging or confirmed by pressure gradient/fractional flow reserve) should be considered for stenting
  • see angioplasty in Management section
• computed tomographic angiography
  • sensitivity suboptimal for detecting distal renal artery stenosis, a common location for fibromuscular dysplasia
• captopril scan for screening (33-47/92-88)*
• doppler ultrasonography of renal arteries (initial imaging)
  • captopril enhanced doppler sonography (63-79/95-80)*
• gadolinium-enhanced magnetic resonance angiography (MRA) (90-95/80-82)*#
• digital subtraction angiography

* sensitivity/specificity (50% - >70% stenosis) relative to angiography

# test of choice, Veterans Administration, Mather

Complications

• unilateral or bilateral renal artery stenosis can cause hypertension refractory to antihypertensives

Management

• NOT ALL cases of hypertension & renal artery stenosis are due to renovascular disease; the two conditions can coexist
• many patients can control blood pressure with medical therapy (primary therapy in most patients)
• angioplasty
  • symptomatic fibromusclar dysplasia without aneurysm or dissection (see fibromusclar dysplasia)
  • angioplasty with stent placement generally no better than medical therapy for atherosclerotic renal artery stenosis
  • see angioplasty with stenting indications for atherosclerotic renal artery stenosis below*
• aggressive control of cardiovascular risk factors
  • control of hypertension
    • ACE inhibitors or ARB (MKSAP20)
    • earlier literature recommends avoiding ACE inhibitors
    • ACE inhibitors may increase serum creatinine levels in patients with bilateral renal artery stenosis, but their effect on ESRD is not as clear
    • monitor serum creatinine in patients with bilateral renal artery stenosis or a single functional kidney
      • check 2 weeks after the addition of an ACE inhibitor or ARB for increase beyond a clinically acceptable level (25%-30%)
  • statins & antiplatelet therapy (clopidogrel or aspirin) may be used to treat peripheral vascular disease
  • control of diabetes mellitus
  • diet & life style measures
    • weight reduction
    • smoking cessation

* angioplasty with stenting indications for atherosclerotic renal artery stenosis

• hemodynamically significant stenoses (>=70% by imaging or confirmed by pressure gradient/fractional flow reserve)
• uncontrolled, resistant, or malignant hypertension or hypertension with intolerance to medication
• flash pulmonary edema or unexplained heart failure
• hemodynamically significant renovascular disease with unstable angina
• acute kidney injury following treatment with an ACE inhibitor or ARB
• progressive impaired kidney function
• angioplasty with stenting less commonly indicated for unilateral stenosis than bilateral stenosis or unilateral stenosis in a patients with a single functioning kidney

More general terms

• arterial stenosis
• visceral arterial disease
• kidney disease; renal disease

More specific terms

• fibromuscular dysplasia

Additional terms

• renal artery