Page created on April 8, 2022. Not updated since.
Introduction and epidemiology
Secondary hypertension is hypertension due to an underlying cause. It accounts for 10% of hypertension cases.
Secondary hypertension should be suspected in:
- Younger patients (<40) with hypertension
- Severe hypertension
- Resistant hypertension
- Obstructive sleep apnoea (OSA)
- Renal parenchymal disease
- Renovascular disease (renal artery stenosis)
- Atherosclerotic renovascular disease
- Fibromuscular dysplasia
- Primary aldosteronism (Conn syndrome)
- Cushing syndrome
- Thyroid disease (hypo or hyper)
The mechanism by which these causes cause secondary hypertension depends on the cause. Some activate RAAS, some activate the sympathetic system, some cause fluid and salt retention, and some function by other mechanisms.
- OSA -> daytime sleepiness, snoring, obesity, non-dipping of BP on ABPM
- Renal parenchymal disease -> abnormal kidney function
- Renovascular hypertension -> abdominal bruit, worsening kidney function after taking RAAS inhibitor, asymmetrical kidney size
- Atherosclerotic renovascular disease -> other features of atherosclerosis
- Fibromuscular dysplasia -> younger women
- Primary aldosteronism -> mostly asymptomatic, some are hypokalaemic
Diagnosis and evaluation
Depends on the suspected cause of the secondary hypertension. Doppler ultrasound for renovascular disease, polysomnography for OSA, etc.
The hypertension itself must be treated, usually with multiple drugs, to prevent complications. The underlying disease should be treated, if possible.