Renal · Hypertension
The facts most likely to be tested
Atherosclerotic renal artery stenosis is the most common cause in older patients with diffuse atherosclerosis.
Fibromuscular dysplasia is the most common cause in young women and typically presents with a 'string of beads' appearance on renal artery angiography.
Renovascular hypertension should be suspected in patients with refractory hypertension despite adherence to three or more antihypertensive medications.
The initiation of ACE inhibitors or ARBs in patients with bilateral renal artery stenosis causes a precipitous drop in glomerular filtration rate and acute kidney injury.
Abdominal bruits heard on physical examination are highly specific but have low sensitivity for renal artery stenosis.
Renal duplex Doppler ultrasonography is the preferred initial screening test for suspected renal artery stenosis.
Renal artery stenting is generally reserved for patients with flash pulmonary edema or refractory heart failure rather than routine blood pressure control.
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A 32-year-old woman presents to the clinic for evaluation of persistent hypertension. She has no significant past medical history and takes no medications. Her blood pressure is 165/98 mmHg. On physical examination, a systolic-diastolic abdominal bruit is heard in the epigastrium. Laboratory studies reveal a serum creatinine of 0.9 mg/dL and a potassium level of 3.4 mEq/L. Renal artery angiography is performed, revealing a 'string of beads' appearance of the right renal artery.
What is the most likely diagnosis?
Fibromuscular dysplasia
The patient's age, gender, and classic angiographic 'string of beads' appearance are pathognomonic for fibromuscular dysplasia, which is a leading cause of secondary hypertension in young women.
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High yield triage
Etiology / Epidemiology
Suspect in atherosclerosis (older males) or fibromuscular dysplasia (young females).
Clinical Manifestations
Look for refractory hypertension and abdominal bruits in the epigastrium.
Diagnosis
Renal artery angiography is the gold standard; CT angiography is the preferred initial imaging.
Treatment
ACE inhibitors are first-line, but contraindicated in bilateral renal artery stenosis.
Prognosis
Risk of flash pulmonary edema and progressive chronic kidney disease if untreated.
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Epidemiology & Etiology
Atherosclerotic disease accounts for 90% of cases, typically in patients >50 with diffuse vascular disease. Fibromuscular dysplasia is the primary cause in women <50, characterized by a string of beads appearance on imaging. Consider this diagnosis in any patient with sudden onset or worsening hypertension.
Pertinent Anatomy
Stenosis occurs in the main renal artery or its branches, leading to renal hypoperfusion. The juxtaglomerular apparatus senses low pressure, triggering the systemic renin-angiotensin-aldosterone cascade.
Pathophysiology
Reduced renal perfusion pressure triggers the release of renin, converting angiotensinogen to angiotensin I. Angiotensin II causes systemic vasoconstriction and stimulates aldosterone release, leading to sodium and water retention. This creates a state of secondary hyperaldosteronism and volume-dependent hypertension.
Clinical Manifestations
Presentation includes resistant hypertension despite three-drug regimens. Listen for abdominal bruits, which are highly specific. Flash pulmonary edema is a classic red flag for bilateral disease or stenosis of a solitary kidney.
Diagnosis
Screening is performed via Duplex Doppler ultrasonography. The Renal artery angiography remains the gold standard for definitive diagnosis. A significant stenosis is typically defined as >70% luminal narrowing.
Treatment
Medical management utilizes ACE inhibitors or ARBs to block the RAAS pathway. Contraindicated in bilateral renal artery stenosis as they precipitate acute renal failure by removing the compensatory efferent arteriolar constriction. Percutaneous transluminal renal angioplasty with stenting is reserved for patients failing medical therapy.
Prognosis
Untreated disease leads to ischemic nephropathy and end-stage renal disease. Monitor serum creatinine closely after initiating ACE inhibitors; a rise of >30% suggests significant bilateral stenosis.
Differential Diagnosis
Primary hyperaldosteronism: hypokalemia without bruits
Pheochromocytoma: episodic palpitations and diaphoresis
Cushing syndrome: moon facies and striae
Coarctation of the aorta: blood pressure differential between arms and legs
Essential hypertension: diagnosis of exclusion in younger patients