What is the initial workup for a patient with secondary hypertension?

Initial Workup for Secondary Hypertension

The initial workup for secondary hypertension should include targeted screening tests based on specific clinical clues, with ambulatory blood pressure monitoring, basic laboratory tests, and evaluation for the most common causes including obstructive sleep apnea, primary aldosteronism, and renovascular disease. 1

When to Suspect Secondary Hypertension

Secondary hypertension should be suspected in patients with:

• Abrupt onset or worsening of hypertension
• Age <35 years with significant hypertension (diastolic >110 mmHg)
• New onset hypertension after age 50
• Resistant hypertension requiring multiple medications
• Malignant hypertension with end-organ damage (BP ≥180/110 mmHg)
• Deterioration of renal function with ACE inhibitors/ARBs
• Presence of abdominal bruits
• Generalized arteriosclerotic occlusive disease 1

Initial Diagnostic Algorithm

Step 1: Confirm True Hypertension

• Perform ambulatory blood pressure monitoring to rule out white-coat hypertension 1
• Ensure proper BP measurement technique with appropriate cuff size

Step 2: Basic Laboratory Evaluation

• Complete blood count
• Basic metabolic panel (sodium, potassium, creatinine, BUN, glucose)
• Urinalysis
• Lipid profile
• Thyroid stimulating hormone (TSH)
• Electrocardiogram 1, 2

Step 3: Targeted Screening Based on Clinical Suspicion

Suspected Cause	Clinical Clues	Recommended Screening Test
Primary aldosteronism	Hypokalemia, resistant hypertension	Aldosterone-to-renin ratio
Renovascular hypertension	Abdominal bruit, deterioration of renal function with ACE inhibitors	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, eGFR
Cushing's syndrome	Central obesity, striae, moon facies	24h urinary free cortisol, dexamethasone suppression
Coarctation of aorta	Upper/lower extremity BP difference, delayed femoral pulses	Echocardiogram, CT angiogram [1]

Prioritizing Evaluation by Prevalence

1. Obstructive Sleep Apnea: Most prevalent secondary cause, present in up to 83% of patients with resistant hypertension 1

   • Screen with validated questionnaires (STOP-BANG, Epworth Sleepiness Scale)
   • Refer for polysomnography when score indicates high risk

2. Primary Aldosteronism: Present in approximately 20% of resistant hypertension cases 1

   • Note: Often does not present with hypokalemia in early stages
   • Morning aldosterone-to-renin ratio after correcting hypokalemia
   • Hold interfering medications (spironolactone, eplerenone) for 4-6 weeks before testing

3. Renovascular Hypertension: Most common type of secondary hypertension in the general population (0.5-5%) 1

   • Renal Doppler ultrasound as initial screening
   • CT or MR angiography for definitive diagnosis

4. Medication-Induced Hypertension: Review all medications and substances

   • NSAIDs, oral contraceptives, corticosteroids, decongestants
   • Recreational drugs (cocaine, amphetamines)
   • Herbal supplements (ephedra, ma huang) 1

Special Considerations

• Age-Specific Approach: Secondary causes are more common in children (<6 years) and young adults (<35 years) 1

• Resistant Hypertension: Always assess medication adherence before extensive workup

  • Consider therapeutic drug monitoring or pill counts
  • Evaluate for white-coat effect with ambulatory monitoring 1

• Cost-Effective Approach: Target testing based on clinical suspicion rather than universal screening

  • Secondary hypertension affects only 5-10% of hypertensive patients 3, 4
  • Early detection is crucial to prevent irreversible vascular remodeling 3

Pitfalls to Avoid

• Failing to confirm true hypertension before extensive workup
• Overlooking medication non-adherence as a cause of apparent resistant hypertension
• Not considering multiple secondary causes that may coexist
• Ignoring drug-induced causes of secondary hypertension
• Expecting complete normalization of blood pressure after treating secondary cause - many patients have residual essential hypertension 3