Renal · Secondary Hypertension
The facts most likely to be tested
Renal artery stenosis is the most common cause of secondary hypertension, typically presenting with a systolic-diastolic abdominal bruit and refractory hypertension.
Primary hyperaldosteronism (Conn syndrome) presents with the classic triad of hypertension, unexplained hypokalemia, and metabolic alkalosis.
Pheochromocytoma is characterized by the classic triad of episodic headaches, diaphoresis, and tachycardia (palpitations) associated with paroxysmal hypertension.
Coarctation of the aorta is identified by brachial-femoral pulse delay and a significant blood pressure discrepancy between the upper and lower extremities.
Obstructive sleep apnea is the most common cause of secondary hypertension in obese patients, often associated with daytime somnolence and snoring.
Cushing syndrome should be suspected in patients with central obesity, moon facies, striae, and proximal muscle weakness alongside elevated blood pressure.
Fibromuscular dysplasia is the most common cause of renal artery stenosis in young women, typically appearing as a string-of-beads appearance on renal angiography.
Vignette unlocked
A 32-year-old woman presents for a routine physical and is found to have a blood pressure of 165/95 mmHg. She has no significant past medical history and takes no medications. Physical examination reveals a systolic-diastolic abdominal bruit heard in the epigastrium. Her serum creatinine is 1.1 mg/dL and potassium is 4.0 mEq/L. A renal artery ultrasound is ordered, which shows a string-of-beads appearance of the 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, a leading cause of secondary hypertension in young women.
Full handout
High yield triage
Etiology / Epidemiology
Suspect in refractory hypertension or onset <30 years. Common causes: Renal artery stenosis, Primary aldosteronism, and Obstructive sleep apnea.
Clinical Manifestations
Look for abdominal bruits in renovascular disease or paroxysmal headaches in pheochromocytoma. Hypokalemia often suggests hyperaldosteronism.
Diagnosis
Screening depends on suspicion; Renal arteriography is the gold standard for renovascular disease. Plasma aldosterone/renin ratio is the initial screen for Conn syndrome.
Treatment
Treat the underlying cause. ACE inhibitors are first-line for unilateral stenosis, but contraindicated in bilateral renal artery stenosis.
Prognosis
High risk for end-organ damage including stroke and heart failure. Early intervention can achieve clinical cure in select surgical candidates.
Full handout
Epidemiology & Etiology
Secondary hypertension accounts for 5-10% of cases. Always screen patients with sudden onset or resistant hypertension (BP uncontrolled on 3+ meds). Common etiologies include chronic kidney disease, coarctation of the aorta, and Cushing syndrome.
Pertinent Anatomy
The juxtaglomerular apparatus regulates renin release in response to renal perfusion. The adrenal cortex (zona glomerulosa) produces aldosterone, while the adrenal medulla secretes catecholamines. Coarctation typically occurs distal to the left subclavian artery.
Pathophysiology
Renovascular disease triggers the Renin-Angiotensin-Aldosterone System (RAAS), causing systemic vasoconstriction and sodium retention. Conn syndrome involves autonomous aldosterone secretion, leading to hypokalemia and metabolic alkalosis. Pheochromocytoma results from excess catecholamines causing episodic vasoconstrictive crises.
Clinical Manifestations
Suspect pheochromocytoma if the triad of headache, palpitations, and diaphoresis is present. Coarctation of the aorta presents with brachial-femoral pulse delay and BP differential between arms and legs. Red flags include hypertensive emergency or sudden worsening of previously stable BP.
Diagnosis
For renovascular hypertension, CT angiography or MRA are preferred initial imaging. Plasma aldosterone/renin ratio >20 is highly suggestive of primary aldosteronism. 24-hour urinary metanephrines are the gold standard for pheochromocytoma.
Treatment
Surgical correction is definitive for renal artery stenosis (stenting) or pheochromocytoma (adrenalectomy). Use spironolactone for primary aldosteronism. Never initiate beta-blockers alone in pheochromocytoma as this causes unopposed alpha-adrenergic vasoconstriction and hypertensive crisis.
Prognosis
Untreated secondary hypertension leads to left ventricular hypertrophy and nephrosclerosis. Long-term monitoring requires serial creatinine and potassium checks to assess for progressive renal damage.
Differential Diagnosis
Renal Artery Stenosis: abdominal bruit
Primary Aldosteronism: hypokalemia
Pheochromocytoma: episodic palpitations
Coarctation of the Aorta: pulse delay
Cushing Syndrome: moon facies/striae