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Updated: Dec 1 2021

Renal Artery Stenosis

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  • Snapshot
    • A 59-year-old man with a history of hypertension presents to his primary care physician for blood pressure management. He has tried lisinopril, hydrochlorothiazide, and losartan, and had minimal effect. He has a strong family history of cardiovascular disease. Physical examination is notable for a bruit in the right flank. Routine bloodwork shows an elevated creatinine. Preparations are made for a doppler ultrasound of the renal arteries.
  • Introduction
    • Clinical definition
      • narrowing of one or both renal arteries
        • this often causes renovascular hypertension
        • grade 1 – RAS (Renal artery stenosis) with no clinical symptoms
        • grade 2 – RAS with controlled hypertension
        • grade 3 – RAS with resistant hypertension, abnormal renal function, or volume overload
  • Epidemiology
    • Prevalence
      • 7% in the United States
      • present in up to 1/3 of patients with malignant or resistant hypertension
    • Demographics
      • atherosclerotic disease
        • patients > 50 years of age
      • fibromuscular dysplasia
        • young women
    • Risk factors
      • atherosclerosis and its risk factors (e.g., smoking and fatty diet)
      • fibromuscular dysplasia
      • kidney transplant patients
      • high calcium or phosphorous levels
      • high low-density lipoprotein cholesterol levels
  • Etiology
    • Pathophysiology
      • narrowing of artery lumen due to
        • atherosclerosis
        • fibromuscular dysplasia
      • narrowed arteries lead to reduced renal perfusion
        • reduced perfusion leads to activation of renin-angiotensin system
          • increased renin → hypertension, hypokalemia, and hypernatremia
        • bilateral renal stenosis can lead to volume overload
          • heart failure
          • pulmonary edema
    • Associated conditions
      • other manifestations of atherosclerotic disease
        • carotid artery disease
        • lower extremity artery disease
        • coronary heart disease
  • Presentation
    • History
      • hypertension before 30 years of age
        • consider fibromuscular dysplasia in young women with abrupt onset of hypertension
      • resistant or malignant hypertension
      • worsening renal function after taking an ACE inhibitor or angiotensin receptor blocking (ARB) agent
        • may indicate bilateral RAS because ACE inhibitors and ARBs further decrease glomerular filtration rate and worsens renal function
      • sudden unexplained volume overload (heart failure or pulmonary edema)
    • Symptoms
      • primary symptoms
        • hypertension
    • Physical exam
      • extremities
        • may have edema if volume overloaded
      • abdomen
        • abdominal or flank bruit through systole and diastole
  • Imaging
    • Ultrasound
      • indications
        • often initial imaging in those < 60 years of age in patients with suspected RAS
      • sensitivity and specificity
        • sensitivity 88-93%
        • specificity 82-89%
    • CT angiography
      • indications
        • in patients with normal renal function and suspected RAS
      • sensitivity and specificity
        • sensitivity 90%
        • specificity 94%
    • MR angiography in patients with renal insufficiency
      • indications
        • in patients with renal insufficiency and suspected RAS
      • sensitivity and specificity
        • sensitivity 75-97%
        • specificity 64-93%
    • Invasive catheter angiography
      • indications
        • only indicated if high suspicion of disease but inconclusive imaging or if revascularization is planned
      • gold standard for diagnosis
  • Studies
    • Labs
      • serum creatinine to assess renal function
        • elevated creatinine may indicate atherosclerosis-associated RAS
        • normal creatinine may indicate fibromuscular dysplasia-associated RAS
      • urine protein to assess renal function
        • typically below nephrotic range (< 3.5 g in 24 hours)

    • Histology
      • fibromuscular dysplasia
        • medial fibroplasia
    • Diagnostic criteria
      • reduction of diameter of > 60%
      • string-of-beads appearance on angiography in fibromuscular dysplasia
  • Differential
    • Essential hypertension
      • typically responsive to therapy
    • Primary hyperaldosteronism
      • high levels of aldosterone
    • Obstructive sleep apnea
      • lethargy and fatigue
  • Treatment
    • Medical
      • ACE-inhibitors or ARBs
        • indications
          • persistent hypertension in patients with RAS
        • contraindicated in bilateral RAS or RAS in patients with single kidney
      • calcium channel blockers or β-blockers
        • given if patients do not respond to ACE-inhibitors or ARBs
      • manage lipid disorders with statins
    • Operative
      • revascularization
        • indications
          • severe complications of RAS
            • unexplained heart failure
            • unexplained pulmonary edema
            • chronic kidney disease
            • inadequately controlled hypertension
        • outcomes
          • may not improve outcomes in those with atherosclerotic RAS
          • cures up to 58% of hypertension in patients with fibromuscular dysplasia-associated RAS
        • complications
          • contrast-induced acute kidney injury or allergic reaction (< 3%)
          • bleeding, hematoma, or arteriovenous fistula
  • Complications
    • Renal dysfunction can progress to end-stage renal disease
      • incidence
        • 4% in one study of 68 adults over 39 months
      • treatment
        • dialysis and kidney transplant
  • Prognosis
    • Prognostic variable
      • negative
        • elevated serum creatinine
        • comorbid heart disease
        • comorbid chronic obstructive pulmonary disease (COPD)
    • Survival with treatment
      • 91% at 1 year
      • 67% at 5 years
      • 41% at 10 years
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