Most Common Cause of Secondary Hypertension in Adults
Renal parenchymal disease is the most common cause of secondary hypertension in adults, accounting for the majority of identifiable cases. 1
Prevalence and Ranking of Secondary Causes
The hierarchy of secondary hypertension causes is well-established in current guidelines:
- Renal parenchymal disease represents the most frequent cause overall, with a prevalence of 1-2% in the general hypertensive population 2, 1, 3
- Renovascular disease is the second most common cause, affecting 5-34% depending on the clinical context (particularly in resistant hypertension) 1, 3
- Primary aldosteronism affects 8-20% of patients with resistant hypertension specifically, making it an important but less frequent cause than renal diseases in the general hypertensive population 1, 3
- Obstructive sleep apnea has a prevalence of 25-50% in resistant hypertension cases 3
Clinical Recognition of Renal Parenchymal Disease
When evaluating for renal parenchymal disease as the underlying cause, look for these specific indicators:
- History findings: Recurrent urinary tract infections, urinary obstruction, hematuria, urinary frequency and nocturia, analgesic abuse, or family history of polycystic kidney disease 2, 1, 3
- Laboratory abnormalities: Elevated serum creatinine with reduced eGFR, abnormal urinalysis with proteinuria or hematuria 1, 4
- Physical examination: Palpable abdominal mass suggesting polycystic kidney disease, skin pallor from chronic kidney disease 2
Diagnostic Approach
Renal ultrasound is the first-line screening test when renal parenchymal disease is suspected, providing anatomical data on kidney size, cortical thickness, urinary tract obstruction, and renal masses 1
Essential initial laboratory screening includes:
- Serum creatinine with eGFR calculation 1, 4
- Urinalysis with albumin-to-creatinine ratio 1, 4
- Serum electrolytes 1
Important Clinical Context
The prevalence of specific secondary causes varies significantly by clinical presentation:
- In resistant hypertension (requiring ≥3 medications), renovascular disease becomes much more prevalent (5-34%), and primary aldosteronism increases substantially (8-20%) 2, 1, 3
- In younger patients (<30 years), renovascular disease from fibromuscular dysplasia becomes more likely 2
- In older patients (≥65 years), atherosclerotic renovascular disease and renal failure predominate 5
Critical Pitfall to Avoid
Do not assume normal potassium levels exclude secondary causes. Hypokalemia is often absent in primary aldosteronism, and normal potassium does not exclude this diagnosis 3. Similarly, renal parenchymal disease may present with subtle laboratory abnormalities that progress over time, and delayed diagnosis leads to vascular remodeling and residual hypertension even after treating the underlying cause 4.