Initial Workup for Secondary Hypertension
The initial workup for secondary hypertension should include screening for clinical clues suggesting secondary causes, comprehensive medical and family history, physical examination, and targeted diagnostic tests based on suspected underlying causes. 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
- Age of onset younger than 30 years (especially before puberty)
- Malignant or accelerated hypertension 1, 2
Initial Evaluation
History and Physical Examination
- Document duration of hypertension, previous BP readings, treatments and responses
- Obtain 3-generation family history of hypertension
- Assess cardiovascular risk factors (diabetes, dyslipidemia, CKD, smoking, diet, alcohol)
- Look for symptoms suggesting specific causes:
- Episodic headaches, palpitations, sweating (pheochromocytoma)
- Snoring, daytime sleepiness (obstructive sleep apnea)
- Muscle weakness, polyuria (hyperaldosteronism)
- Weight gain, hirsutism, easy bruising (Cushing syndrome)
- Physical examination should include:
- BP measurement in both arms
- Fundoscopy for hypertensive retinopathy
- Abdominal examination for renal bruits
- Assessment for features of endocrine disorders 1
Basic Laboratory Tests
- Complete blood count
- Serum electrolytes, creatinine, eGFR
- Fasting glucose
- Lipid profile
- Liver function tests
- Urinalysis and urine albumin-to-creatinine ratio
- 12-lead ECG 1
Targeted Diagnostic Tests Based on Suspected Cause
The American Heart Association recommends the following diagnostic approach for suspected causes of secondary hypertension:
| Suspected Cause | Recommended Screening Test |
|---|---|
| Primary aldosteronism | Aldosterone-to-renin ratio |
| Renovascular hypertension | Renal Doppler ultrasound, CT/MR angiography |
| Pheochromocytoma | 24h urinary/plasma metanephrines and normetanephrines |
| Obstructive sleep apnea | Overnight polysomnography |
| Renal parenchymal disease | Renal ultrasound, urinalysis, eGFR |
| Cushing's syndrome | 24h urinary free cortisol, dexamethasone suppression |
| Thyroid disease | TSH |
| Hyperparathyroidism | PTH, calcium, phosphate |
| Coarctation of aorta | Echocardiogram, CT angiogram |
Age-Based Approach
The prevalence and etiology of secondary hypertension vary by age:
Children and adolescents: Up to 85% have an identifiable cause, most commonly renal parenchymal disease. All children with confirmed hypertension should undergo renal ultrasonography 3
Young adults (especially women): Consider fibromuscular dysplasia causing renal artery stenosis, which can be detected by abdominal MRI or CT 3
Middle-aged adults: Primary aldosteronism is most common; initial diagnostic test is aldosterone/renin ratio 3
Older adults: Atherosclerotic renal artery stenosis, renal failure, and hypothyroidism are common causes 2
Common Pitfalls and Caveats
Verify medication adherence before extensive workup for secondary causes, as non-adherence is a common cause of apparent resistant hypertension 1
Rule out white coat effect with ambulatory BP monitoring before diagnosing true resistant hypertension 1
Maintain BP control with appropriate antihypertensive medications during diagnostic workup 1
Consider referral to specialists for complex cases or when specialized testing is required 1, 4
Early detection and treatment are crucial as BP rarely returns to normal even after treating the secondary cause due to vascular remodeling 5
Remember prevalence: Secondary hypertension affects only 5-10% of all hypertensive patients, so targeted screening based on clinical suspicion is more efficient than universal screening 4, 5, 6