What is the workup for secondary hypertension (htn)?

Workup for Secondary Hypertension

The comprehensive workup for secondary hypertension should include screening for clinical clues (early onset, resistant hypertension, sudden BP deterioration), targeted laboratory testing, and appropriate imaging based on suspected etiology. 1

When to Suspect Secondary Hypertension

Secondary hypertension should be considered in patients with:

• Early onset hypertension (especially <30 years of age)
• Resistant hypertension despite optimal therapy
• Sudden deterioration in previously well-controlled BP
• Hypertensive urgency or emergency
• Strong family history suggesting monogenic forms
• Age of onset younger than 30 years (especially before puberty)
• Presence of target organ damage disproportionate to BP levels 1, 2

Initial Evaluation

1. Confirm true hypertension:

   • Verify proper BP measurement technique
   • Rule out white coat effect with ambulatory BP monitoring
   • Assess medication adherence
   • Review current antihypertensive regimen 1

2. Comprehensive history:

   • Duration of hypertension
   • Previous BP readings and treatments
   • 3-generation family history of hypertension
   • Risk factors (cardiovascular disease, diabetes, kidney disease)
   • Medication review (including OTC and recreational substances)
   • Symptoms suggesting specific causes (e.g., flushing, sweating) 1

3. Basic laboratory tests:

   • Complete blood count
   • Serum electrolytes, creatinine, eGFR
   • Fasting glucose
   • Lipid profile
   • Liver function tests
   • Urinalysis and albumin-to-creatinine ratio 1

Targeted Workup Based on Suspected Cause

Primary Aldosteronism

• Screening test: Aldosterone-to-renin ratio
• Confirmatory tests: Salt loading test, captopril challenge
• When to suspect: Hypokalemia, resistant hypertension, adrenal incidentaloma 1, 2

Renovascular Hypertension

• Screening tests: Renal Doppler ultrasound, CT/MR angiography
• When to suspect: Abdominal bruit, severe hypertension with unilateral smaller kidney, ≥50% increase in creatinine after ACE inhibitor/ARB initiation, recurrent flash pulmonary edema 1, 2

Pheochromocytoma

• Screening test: 24-hour urinary or plasma metanephrines and normetanephrines
• When to suspect: Paroxysmal symptoms (headaches, palpitations, sweating), labile BP, family history of endocrine tumors 1

Obstructive Sleep Apnea

• Screening test: Overnight polysomnography
• When to suspect: Snoring, witnessed apneas, daytime somnolence, obesity 1, 3

Renal Parenchymal Disease

• Screening tests: Renal ultrasound, urinalysis, eGFR
• When to suspect: Abnormal urinalysis, elevated creatinine, family history of kidney disease 1

Cushing's Syndrome

• Screening test: 24-hour urinary free cortisol, overnight dexamethasone suppression
• When to suspect: Central obesity, moon facies, striae, easy bruising 1

Thyroid Disease

• Screening test: TSH
• When to suspect: Symptoms of hypo/hyperthyroidism 1

Hyperparathyroidism

• Screening tests: PTH, calcium, phosphate
• When to suspect: Hypercalcemia, osteoporosis, kidney stones 1

Coarctation of Aorta

• Screening tests: Echocardiogram, CT angiogram
• When to suspect: BP differential between arms and legs, delayed femoral pulses, systolic murmur 1, 4

Age-Based Considerations

• Children and young adults: Focus on renal parenchymal disease, coarctation of aorta, and in young women, fibromuscular dysplasia 4
• Middle-aged adults: Primary aldosteronism is most common 4
• Older adults: Atherosclerotic renal artery stenosis, renal failure, and thyroid disorders 2, 4

Common Pitfalls and Caveats

1. Medication non-adherence: Always assess medication adherence before extensive workup for secondary causes 1

2. Substance-induced hypertension: Review all medications (prescription and OTC), supplements, and recreational substances that may elevate BP 1, 2

3. White coat hypertension: Confirm with out-of-office measurements before extensive workup 1

4. Delayed diagnosis: Secondary hypertension affects 5-10% of hypertensive patients and early detection is crucial to prevent irreversible vascular changes 5, 3

5. Residual hypertension: Despite appropriate treatment of secondary causes, BP may not return to normal due to concomitant essential hypertension or irreversible vascular remodeling 3

Remember that while secondary hypertension workup can be resource-intensive, correct identification of underlying causes can lead to more effective, potentially curative management and subsequent cardiovascular risk reduction 5.