What is the approach to screening for secondary hypertension?

Screening for Secondary Hypertension

Screen for secondary hypertension selectively in patients with specific clinical red flags rather than routinely in all hypertensive patients, as secondary causes affect only 5-10% of the general hypertensive population but increase to 10-20% in resistant cases. 1, 2

Who to Screen: Clinical Red Flags

Target your screening to patients with these high-risk features:

• Age of onset <30 years (or <40 years per ESC 2024) - suggests fibromuscular dysplasia, coarctation, or endocrine disorders 1, 3
• Resistant hypertension - BP >140/90 mmHg despite optimal doses of ≥3 antihypertensive drugs including a diuretic 1, 2
• Abrupt onset or sudden deterioration of previously controlled hypertension 1, 2
• Hypertensive urgency or emergency 1
• Target organ damage disproportionate to duration or severity of hypertension 1

Initial Screening Approach

Basic Laboratory Panel (All Suspected Cases)

Perform these tests universally when secondary hypertension is suspected 1, 2:

• Serum sodium and potassium
• Serum creatinine and eGFR
• Urinalysis with dipstick for blood and protein
• Urinary albumin-to-creatinine ratio
• Fasting blood glucose or HbA1c
• Thyroid-stimulating hormone (TSH)
• 12-lead ECG

Major 2024 guideline change: The ESC now recommends measuring renin and aldosterone in all adults with confirmed hypertension (Class IIa recommendation), representing a significant shift from traditional selective screening. 1

Targeted Physical Examination Findings

Look for these specific clues 1, 3:

• Radio-femoral delay - coarctation of the aorta
• Abdominal systolic-diastolic bruit - renovascular disease
• Truncal obesity with purple striae - Cushing syndrome
• Enlarged kidneys on palpation - polycystic kidney disease
• Snoring, daytime sleepiness, obesity - obstructive sleep apnea (present in 25-50% of resistant hypertension) 1

Cause-Specific Screening Algorithms

Primary Aldosteronism (8-20% of Resistant Hypertension)

Screen when you find 1, 2:

• Resistant hypertension with spontaneous or diuretic-induced hypokalemia
• Muscle cramps or weakness
• Family history of early-onset hypertension or stroke at young age

Testing sequence:

1. Plasma aldosterone-to-renin ratio (initial screening - now recommended for all confirmed hypertension per ESC 2024) 1
2. Confirmatory testing: IV saline suppression test or oral sodium loading test 2
3. CT adrenal imaging for localization 2
4. Adrenal vein sampling if surgical intervention considered 2

Renovascular Disease (5-34% in Selected Populations)

Screen when you find 1, 2:

• Abrupt onset or worsening hypertension
• Flash pulmonary edema
• Early-onset hypertension, especially in women (fibromuscular dysplasia)
• Abdominal bruits

Testing sequence:

1. Renal ultrasound with Duplex Doppler (initial) 2
2. CT or MR renal angiography (confirmation) 1, 2

Renal Parenchymal Disease (1-2% Prevalence)

Screen when you find 1, 2:

• History of urinary tract infections, obstruction, hematuria
• Urinary frequency, nocturia
• Analgesic abuse
• Family history of polycystic kidney disease

Testing: Already captured in basic screening (creatinine, eGFR, urinalysis) 2

Obstructive Sleep Apnea (25-50% of Resistant Hypertension)

Screen when you find 1:

• Snoring, daytime sleepiness, obesity
• Non-dipping nocturnal BP pattern on 24-hour ambulatory monitoring

Testing sequence:

1. Home sleep apnea testing 2
2. Overnight polysomnography (gold standard) 2

Pheochromocytoma (Uncommon but Dangerous)

Screen when you find 1:

• Episodic symptoms (headaches, palpitations, sweating)
• Labile hypertension

Testing sequence:

1. 24-hour urinary catecholamines or metanephrines 1
2. Abdominal/adrenal imaging 1

Critical Pitfalls to Avoid

• Don't perform expensive imaging before completing basic laboratory screening - this wastes resources and delays diagnosis 1
• Don't miss medication-induced hypertension - review all medications (including NSAIDs, oral contraceptives, decongestants) before extensive workup 1
• Don't delay diagnosis - vascular remodeling occurs with prolonged untreated secondary hypertension, leading to residual hypertension even after treating the underlying cause 2, 4
• Don't assume cure after treatment - many patients require ongoing antihypertensive therapy even after addressing the secondary cause due to irreversible vascular changes 1, 4

When to Refer

Refer to specialist centers when 3:

• Positive screening tests for secondary hypertension requiring confirmatory testing
• Complex cases requiring specialized expertise
• Resistant hypertension uncontrolled despite optimal medical therapy

Role of 24-Hour Ambulatory BP Monitoring

Ambulatory BP monitoring plays a central role in the workup of suspected secondary hypertension, particularly for identifying non-dipping patterns suggestive of obstructive sleep apnea and for confirming true resistant hypertension versus white-coat effect. 4