What are the diagnostic approaches to identify secondary causes of hypertension?

From the Guidelines

To investigate secondary causes of hypertension, a thorough clinical evaluation including a detailed medical history, physical examination, and basic laboratory tests is essential, as recommended by the most recent guidelines 1. When evaluating patients with hypertension, it is crucial to look for clinical clues such as resistant hypertension, sudden onset of hypertension, age of onset <30 or >55 years, and absence of family history. Initial laboratory tests should include:

• Complete blood count
• Basic metabolic panel
• Urinalysis
• Thyroid function tests
• Electrocardiogram For suspected renovascular hypertension, order a renal ultrasound with Doppler studies or CT angiography, as suggested by the 2024 ESC guidelines 1. To evaluate primary aldosteronism, measure the aldosterone-to-renin ratio after discontinuing interfering medications (if possible) for 2-4 weeks, which can provide helpful information, especially when reviewing prior potassium levels (hypokalaemia increases the likelihood of coexistent primary hyperaldosteronism) 1. For pheochromocytoma, measure plasma free metanephrines or 24-hour urinary metanephrines and catecholamines, as recommended by the 2024 ESC guidelines 1. Cushing's syndrome evaluation includes overnight dexamethasone suppression test (1 mg at 11 PM with cortisol measurement at 8 AM the next day) or 24-hour urinary free cortisol, which are useful screening tests 1. Sleep apnea screening should be considered in patients with obesity, snoring, or daytime somnolence, using overnight ambulatory polysomnography as a screening test 1. Secondary hypertension affects approximately 10-15% of hypertensive patients, and identifying these causes is crucial because specific treatments can potentially cure the hypertension or significantly improve blood pressure control, ultimately reducing morbidity, mortality, and improving quality of life 1.

From the Research

Investigation of Secondary Causes of Hypertension

To investigate secondary causes of hypertension, the following steps can be taken:

• Identify patients with suggestive presentations, such as early-onset, severe or resistant hypertension, or those with a suggestive family history or clinical clues 2
• Take a thorough history and perform a physical examination to look for clinical clues 2, 3
• Conduct laboratory tests, including:
  • Electrolytes, urea, creatinine, and the aldosterone:renin ratio 2
  • Urinalysis and the urine albumin:creatinine ratio 2
• Interpret abnormal results and prompt further investigation if necessary 2
• Consider specialist advice if needed 2

Common Causes of Secondary Hypertension

Common causes of secondary hypertension include:

• Renal disease, such as chronic parenchymal disease and renovascular hypertension 4, 3, 5
• Endocrinopathies, such as primary aldosteronism, pheochromocytoma, or thyroid disease 4, 3, 5
• Obstructive sleep apnea 4, 2, 5
• Drug-induced hypertension 4, 2, 5
• Substance abuse 3

Evaluation and Management

The evaluation and management of secondary hypertension should be guided by the clinician's index of suspicion and interpretation of data 3

• Selection of patients for testing should incorporate historical and clinical clues, previous treatment course, and comorbidities 6
• Decisions regarding the extent of secondary evaluation require consideration of the likelihood of diagnosis, the patient's overall health status and prognosis, and balancing the risks of intervention against the risks of missing a diagnosis 6