Cardiovascular · Year 1 · from Cardiovascular

Case 2: Renovascular Hypertension - Renal Artery Stenosis

Patient Presentation

Demographics: 62-year-old male

Chief Complaint: Difficult-to-control hypertension

History of Present Illness: A 62-year-old male with 15-year history of hypertension, diabetes, and hyperlipidemia presents for evaluation of refractory hypertension. Despite taking lisinopril 40 mg, amlodipine 10 mg, and hydrochlorothiazide 25 mg, his BP remains 175/105 mmHg. He has had progressive decline in kidney function over the past year. He reports a recent episode of acute pulmonary edema ("flash pulmonary edema") that resolved with diuresis. Heavy smoker (50 pack-years).

Physical Examination:

  • Vital Signs: BP 178/108 mmHg (both arms equal), HR 72 bpm, RR 16/min
  • General: Obese male, appears older than stated age
  • Cardiovascular: Regular rhythm, S4 gallop, abdominal bruit (right periumbilical)
  • Peripheral vascular: Diminished femoral pulses, ABI 0.7 bilateral
  • Fundoscopy: Arteriovenous nicking, copper wiring (hypertensive retinopathy)

Workup

  • Labs:
  • Creatinine: 2.1 mg/dL (was 1.3 one year ago)
  • Potassium: 3.2 mEq/L (low - secondary hyperaldosteronism)
  • BUN: 38 mg/dL
  • Plasma renin activity: 12 ng/mL/hr (elevated)
  • Aldosterone: 28 ng/dL (elevated)
  • Renal Doppler ultrasound: Right kidney 8.5 cm (small), left 11 cm; elevated resistive indices
  • CT angiography: 85% stenosis of right renal artery, moderate left renal artery stenosis (60%)
  • Renal artery duplex: Peak systolic velocity 380 cm/s in right renal artery (normal <180)

Diagnosis

Atherosclerotic bilateral renal artery stenosis with secondary renovascular hypertension

Blood Pressure Regulation Correlation:

RAAS Activation in Renal Artery Stenosis:

  1. Stenosis → ↓ renal perfusion pressure
  2. Juxtaglomerular cells sense low pressure → ↑ renin secretion
  3. Renin converts angiotensinogen → angiotensin I
  4. ACE converts angiotensin I → angiotensin II
  5. Angiotensin II effects:
  • Vasoconstriction → ↑ SVR → ↑ BP
  • Aldosterone release → Na+/H2O retention → ↑ volume → ↑ BP
  • ADH release → H2O retention
  • Sympathetic activation

Flash pulmonary edema: Sudden volume and pressure overload overwhelms cardiac reserve

Hypokalemia: Due to secondary hyperaldosteronism (aldosterone promotes K+ excretion)

ACE inhibitor caution: Can cause acute kidney injury in bilateral RAS (removes angiotensin II-mediated efferent arteriolar constriction that maintains GFR)

Treatment

  1. Medical optimization:
  • Continue calcium channel blocker (amlodipine)
  • Add/continue diuretic
  • Caution with ACE-I/ARB in bilateral disease
  • Statin for atherosclerosis
  1. Revascularization options:
  • Renal artery stenting (angioplasty with stent)
  • Surgical revascularization (bypass)
  • Indicated for: flash pulmonary edema, progressive CKD, refractory hypertension
  1. Risk factor modification:
  • Smoking cessation (critical)
  • Diabetes control
  • Lipid management

Clinical Image

Image Description: Renal angiogram demonstrating severe stenosis of the renal artery with characteristic narrowing and post-stenotic dilation. The stenosis is typically located at the ostium or proximal segment in atherosclerotic disease.

Source: Wikimedia Commons - Renal artery stenosis License: CC BY-SA 3.0 URL: https://commons.wikimedia.org/wiki/File:Renal_artery_stenosis.jpg

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