Updated: 11/5/2018

Renal Artery Stenosis

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Snapshot
  • A 23-year-old woman with no significant past medical history presents to her primary care physician for an annual physical exam.  She was found to have a blood pressure of 156/94 mmHg. She has never had any episodes of high blood pressure in the past and she has no family history of hypertension. She is prescribed captopril. After two weeks, she presents to the emergency room with hypertensive urgency. Captopril was immediately stopped and after stabilizing her blood pressure, an ultrasound revealed bilateral renal artery stenosis.
Introduction
  • Clinical definition
    • renal artery stenosis (RAS) occurs when one or both of the renal arteries are narrowed
      • this often causes renovascular hypertension
  • 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
      • in kidney transplant patients
      • high calcium or phosphorous levels
      • high low-density lipoprotein cholesterol levels
  • Pathogenesis
    • 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
      • if abrupt onset in a young women, consider fibromuscular dysplasia
    • resistant or malignant hypertension
    • worsening renal function after taking an ACE inhibitor or angiotensin receptor blocking (ARB) agent
      • may indicate bilateral renal artery stenosis (RAS) because ACE inhibitors and ARBs further decrease glomerular filtration rate and worsen renal function
    • sudden unexplained volume overload (heart failure or pulmonary edema)
  • Physical exam
    • extremities
      • may have edema if volume overloaded
    • abdomen
      • abdominal or flank bruit through systole and diastole
    • vitals
      • hypertension
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
    • indications
      • in patients with renal insufficiency and suspected RAS
    • sensitivity and specificity
      • sensitivity 75-97%
      • specificity 64-93%
Studies
  • This clinical image of angiogram shows the string-of-beads appearance of fibromuscular dysplasia.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)
  • Invasive catheter angiography
    • gold standard for diagnosis
    • only indicated if high suspicion of disease but inconclusive imaging or if revascularization is planned
  • 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
      • 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
  • 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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Questions (3)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
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