From the Guidelines
The investigation of secondary hypertension should begin with a thorough clinical assessment to identify patients who warrant further evaluation, as recommended by the 2024 ESC guidelines for the management of elevated blood pressure and hypertension 1.
Initial Screening
Initial screening should include a detailed medical history focusing on symptoms suggesting specific causes, medication review to identify drugs that may elevate blood pressure, physical examination looking for signs like abdominal bruits or cushingoid features, and basic laboratory tests including:
- Serum electrolytes
- Creatinine
- Estimated glomerular filtration rate
- Urinalysis
- Blood glucose
Targeted Investigations
For patients with suggestive findings, targeted investigations should be pursued based on the suspected cause.
- For primary aldosteronism, measure the aldosterone-to-renin ratio after adjusting interfering medications.
- For renal artery stenosis, consider duplex Doppler ultrasonography, CT angiography, or magnetic resonance angiography.
- Pheochromocytoma evaluation includes measuring plasma free metanephrines or 24-hour urinary metanephrines and catecholamines.
- Cushing's syndrome screening involves overnight dexamethasone suppression test or 24-hour urinary free cortisol.
- Obstructive sleep apnea may require polysomnography, while thyroid function tests can identify thyroid disorders.
Prioritization of Investigations
The timing of these investigations should be prioritized based on clinical suspicion, with more invasive tests reserved for when non-invasive screening is positive or clinical suspicion remains high, as suggested by the 2020 International Society of Hypertension global hypertension practice guidelines 1. This systematic approach is essential because identifying and treating the underlying cause of secondary hypertension can potentially cure the hypertension or significantly improve blood pressure control. According to the 2024 ESC guidelines, routine genetic testing for patients with hypertension is not recommended, but patients with hypertension presenting with suggestive signs, symptoms, or medical history of secondary hypertension should be appropriately screened for secondary hypertension 1.
From the Research
Approach to Investigating Secondary Hypertension
The approach to investigating secondary hypertension involves a combination of clinical evaluation, laboratory tests, and imaging studies.
- The assessment of patients begins with history taking and examination to look for clinical clues, such as early-onset, severe or resistant hypertension, and a suggestive family history 2.
- Laboratory tests include electrolytes, urea, creatinine, and the aldosterone:renin ratio, urinalysis, and the urine albumin:creatinine ratio 2.
- Abnormal results should prompt further investigation, and specialist advice can be sought if needed 2.
Common Causes of Secondary Hypertension
The most common causes of secondary hypertension include:
- Renal disease 2, 3, 4, 5
- Primary aldosteronism 2, 6, 3, 4, 5
- Obstructive sleep apnea 2, 5
- Medicines, illicit substances, and alcohol 2
- Renal artery stenosis 6, 3, 4, 5
- Atherosclerotic renal artery stenosis 3, 4
- Fibromuscular dysplasia 3
- Pheochromocytoma 3, 4, 5
- Cushing syndrome 5
- Thyroid disease 5
- Coarctation of the aorta 3, 4, 5
Diagnostic Tests
Diagnostic tests for secondary hypertension include:
- Aldosterone:renin ratio 2, 6, 3
- Adrenal venous sampling 6
- Imaging examinations, such as abdominal magnetic resonance imaging or computed tomography 3
- Renal ultrasonography 3
- Directed imaging, such as aortic coarctation, renal vascular hypertension, and endocrine causes 4
Treatment
Treatment of secondary hypertension depends on the underlying cause and may involve: