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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
  • renal artery stenosisClinical 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
  • Pathophysiology
    • 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
  • 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
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
 
 

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