Initial Workup for Secondary Hypertension
The initial workup for secondary hypertension should include routine tests (complete blood count, serum creatinine, eGFR, electrolytes, fasting glucose, lipid profile, urinalysis, albumin-to-creatinine ratio, and 12-lead ECG) followed by targeted screening tests based on clinical suspicion of specific causes. 1
Clinical Indicators for Secondary Hypertension
Secondary hypertension affects approximately 10% of adults with hypertension 2 and requires a systematic approach to diagnosis. Consider secondary causes when encountering:
- Early-onset hypertension (<30 years)
- Severe hypertension (>180/110 mmHg)
- Resistant hypertension (BP uncontrolled on ≥3 medications)
- Sudden worsening of previously controlled hypertension
- Presence of hypertension-mediated organ damage
- Strong family history suggesting monogenic forms
- Poor response to conventional therapy
Initial Diagnostic Tests
The European Society of Cardiology and American Heart Association recommend the following initial tests for all patients with suspected secondary hypertension 3, 1:
Laboratory tests:
- Complete blood count
- Serum creatinine and eGFR
- Electrolytes (sodium, potassium, chloride)
- Fasting glucose
- Lipid profile
- Liver function tests
- Urinalysis
- Albumin-to-creatinine ratio
Other initial tests:
- 12-lead ECG (to detect atrial fibrillation and left ventricular hypertrophy)
- Fundoscopy (to detect hypertensive retinopathy)
Targeted Screening Based on Suspected Cause
After initial workup, additional targeted tests should be ordered based on clinical suspicion 1:
| Suspected Cause | Clinical Clues | Recommended Screening Test |
|---|---|---|
| Primary aldosteronism | Hypokalemia, resistant hypertension | Aldosterone-to-renin ratio |
| Renovascular hypertension | Abdominal bruit, flash pulmonary edema | Renal Doppler ultrasound, CT/MR angiography |
| Pheochromocytoma | Episodic symptoms (headache, sweating, palpitations) | 24h urinary/plasma metanephrines and normetanephrines |
| Obstructive sleep apnea | Snoring, daytime somnolence, obesity | Overnight polysomnography |
| Renal parenchymal disease | Abnormal urinalysis, elevated creatinine | Renal ultrasound, urinalysis, eGFR |
| Cushing's syndrome | Central obesity, striae, moon facies | 24h urinary free cortisol, dexamethasone suppression |
| Thyroid disease | Tachycardia, tremor, weight changes | TSH |
| Hyperparathyroidism | Hypercalcemia, osteoporosis | PTH, calcium, phosphate |
| Coarctation of aorta | BP differential between arms and legs | Echocardiogram, CT angiogram |
Important Considerations
Medication assessment: Always evaluate current medications and substances that may cause or worsen hypertension, including NSAIDs, oral contraceptives, sympathomimetics, steroids, and illicit drugs 1, 4
Timing of testing: Initial testing for primary aldosteronism (aldosterone-to-renin ratio) is best performed before starting potentially interfering antihypertensive medications 4
Medication interference: If the patient is already taking medications that interfere with testing (especially for primary aldosteronism), interpretation must consider these effects or medications may need to be temporarily adjusted 4
Specialist referral: Consider referral to specialists with expertise in treating specific secondary causes when identified 2
Common Pitfalls to Avoid
Overlooking common causes: Primary aldosteronism and obstructive sleep apnea are frequently underdiagnosed despite being common causes of secondary hypertension 5
Premature conclusion: Even after treating the secondary cause, blood pressure may not normalize completely due to concomitant essential hypertension or irreversible vascular remodeling 6
Delayed diagnosis: Early detection and treatment are crucial to prevent irreversible vascular changes and target organ damage 6
Poor adherence assessment: Always assess medication adherence before extensive workup for secondary causes 1
Ignoring drug-induced causes: Failure to recognize medications or substances as potential causes of secondary hypertension can lead to unnecessary testing 4
By following this systematic approach to the initial workup of secondary hypertension, clinicians can efficiently identify potentially reversible causes and improve patient outcomes through targeted treatment.