What is the workup for secondary hypertension?

Workup for Secondary Hypertension

The workup for secondary hypertension should include a thorough assessment of clinical clues, basic screening tests, and targeted investigations based on initial findings, with referral to specialist centers for complex cases. 1, 2

When to Suspect Secondary Hypertension

• Screen for secondary hypertension in patients with early-onset hypertension (<30 years of age), resistant hypertension, sudden deterioration in BP control, hypertensive urgency/emergency, or strong clinical clues suggesting secondary causes 1, 2
• Secondary hypertension affects 5-10% of all hypertensive patients and is potentially curable if identified early 1, 3
• Common causes include renal parenchymal disease, renovascular hypertension, primary aldosteronism, obstructive sleep apnea, and substance/drug-induced hypertension 1

Initial Screening and Basic Workup

• Basic screening should include:
  • Thorough history and physical examination focusing on symptoms and signs of secondary causes 1, 2
  • Basic blood biochemistry including sodium, potassium, serum creatinine, eGFR, and TSH 1
  • Urinalysis to detect proteinuria, hematuria, or other abnormalities 1, 2
  • 12-lead ECG to detect atrial fibrillation, left ventricular hypertrophy, or ischemic heart disease 1
  • Fasting blood glucose or HbA1c and lipid profile if available 1, 2

Physical Examination Focus Areas

• Circulation and heart: Pulse rate/rhythm/character, jugular venous pressure, apex beat, extra heart sounds, basal crackles, peripheral edema, bruits (carotid, abdominal, femoral) 1
• Other systems: Enlarged kidneys, neck circumference >40 cm (obstructive sleep apnea), enlarged thyroid, increased BMI/waist circumference, fatty deposits and colored striae (Cushing syndrome) 1, 2

Targeted Investigations Based on Clinical Suspicion

For Renal Parenchymal Disease

• Kidney ultrasound to assess kidney size, structure, and evidence of obstruction 1, 2
• Urinary albumin/creatinine ratio 1, 2

For Renovascular Hypertension

• Duplex ultrasound, abdominal CT or MR angiography depending on availability and renal function 1, 2
• Consider in patients with abrupt onset or worsening hypertension, flash pulmonary edema, or early-onset hypertension 2

For Primary Aldosteronism

• Plasma aldosterone-to-renin ratio as initial screening test 2, 4
• Confirmatory testing (e.g., intravenous saline suppression test) 1, 2
• Adrenal imaging (CT) and adrenal vein sampling if positive 1, 2
• Consider in patients with hypokalemia, resistant hypertension, or family history of early-onset hypertension 2

For Pheochromocytoma

• Plasma free metanephrines or 24-hour urinary metanephrines 1, 2
• Abdominal/adrenal imaging if biochemical tests are positive 1, 2
• Consider in patients with episodic symptoms, labile hypertension, or family history of pheochromocytoma 2

For Obstructive Sleep Apnea

• Home sleep apnea testing (level 3 sleep study) or overnight polysomnography 1, 2
• Consider in patients with snoring, daytime sleepiness, obesity, and non-dipping nocturnal BP pattern 2

For Cushing Syndrome

• Dexamethasone suppression tests and 24-hour urinary free cortisol 1, 4
• Abdominal/pituitary imaging if biochemical tests are positive 1

For Coarctation of the Aorta

• Echocardiogram 1, 5
• CT or MR angiogram if echocardiogram is suggestive 1

Additional Imaging When Indicated

• Echocardiography: To detect LVH, systolic/diastolic dysfunction, atrial dilation, aortic coarctation 1
• Carotid ultrasound: To identify plaques or stenosis 1
• Fundoscopy: To detect retinal changes, hemorrhages, papilledema 1
• Brain CT/MRI: For suspected hypertension-related brain injury 1

Common Pitfalls to Avoid

• Failing to exclude pseudoresistant hypertension and drug/substance-induced hypertension before extensive workup for secondary causes 1, 2
• Performing expensive imaging studies before completing basic laboratory screening 2
• Overlooking common medications that can cause or exacerbate hypertension (NSAIDs, oral contraceptives, sympathomimetics, glucocorticoids) 2, 6

Referral Considerations

• Consider referring patients with suspected secondary hypertension to specialist centers with appropriate expertise and resources 1, 2
• Resistant hypertension should be managed in specialist centers with sufficient expertise and resources 1

Algorithm for Secondary Hypertension Workup

1. Identify clinical clues suggesting secondary hypertension 1, 2
2. Perform basic screening (history, physical exam, basic blood tests, urinalysis) 1
3. Based on initial findings, conduct targeted investigations for specific causes 1, 2
4. Refer to specialists when appropriate 1
5. Implement specific treatment based on identified cause 2