Clinical context
Secondary arterial hypertension corresponds to elevated blood pressure associated with an identifiable and potentially treatable cause. It should be suspected whenever the clinical presentation is atypical or disproportionate, such as early onset, abrupt worsening, very high blood pressure values, treatment resistance or association with suggestive clinical and laboratory abnormalities.
Confirmation of true hypertension
The approach begins by confirming that this is true and persistent hypertension. It is essential to exclude pseudo-resistance, ensuring correct blood pressure measurement technique, use of an appropriate cuff size, optimal dose titration and patient adherence to the prescribed treatment. Ambulatory or home blood pressure monitoring helps exclude the white-coat effect and confirms sustained lack of blood pressure control.
Assessment of iatrogenic causes
Once uncontrolled hypertension has been confirmed, a systematic review of drugs and substances associated with increased blood pressure should be performed. These include non-steroidal anti-inflammatory drugs, corticosteroids, sympathomimetics, hormonal contraceptives, erythropoietin, calcineurin inhibitors, SNRI antidepressants, as well as stimulants, cocaine, amphetamines or supplements with mineralocorticoid effects. Whenever possible, these exposures should be discontinued or replaced.
Initial laboratory and imaging assessment
An initial assessment is then performed to identify guiding clues. This includes serum creatinine and estimated glomerular filtration rate, electrolytes with particular attention to potassium, urinalysis with assessment of albuminuria or proteinuria, fasting glucose or glycated haemoglobin, lipid profile, electrocardiogram and, when indicated, renal ultrasound. These tests help assess target-organ damage and guide aetiological investigation.
Aetiology-directed investigation
Further investigation should be targeted rather than indiscriminate. Renal parenchymal disease is one of the most frequent causes of secondary hypertension and should be considered in the presence of impaired renal function, abnormal urinary sediment or suggestive history. Primary aldosteronism should be suspected in cases of resistant hypertension, spontaneous or diuretic-induced hypokalaemia, severe hypertension or early-onset hypertension, with the aldosterone-renin ratio as the initial screening test.
Renovascular hypertension
Renovascular hypertension should be considered in cases of abrupt onset or rapid worsening of blood pressure, abdominal bruit, renal asymmetry, deterioration of renal function after initiation of renin-angiotensin system inhibitors or episodes of acute pulmonary oedema. Imaging assessment should be selected according to the clinical context and renal function.
Obstructive sleep apnoea syndrome
Obstructive sleep apnoea syndrome is a frequent and often underdiagnosed cause of secondary hypertension. It should be suspected in patients with habitual snoring, daytime sleepiness, obesity, large neck circumference or a non-dipper or reverse-dipper pattern on ambulatory blood pressure monitoring.
Less frequent endocrine causes
In selected situations, less frequent endocrine causes should be considered, such as thyroid dysfunction, hypercortisolism, pheochromocytoma or coarctation of the aorta, according to specific clinical clues. Diagnostic confirmation and subtyping should be performed in a specialist setting.
Conclusion and follow-up
In the absence of an identifiable secondary cause, essential hypertension is not excluded, and treatment optimisation with regular follow-up should be maintained. However, correct identification of secondary hypertension allows a targeted and, in some cases, potentially curative approach, with significant impact on blood pressure control and long-term prognosis.
