Investigations to exclude secondary hypertension

Additional investigations to exclude a secondary cause of hypertension might include:

• serum potassium - hypokalaemia may indicate diuretics, Conn's syndrome, renovascular disease, Cushing's syndrome
• serum calcium - for hypercalcaemia
• thyroid function tests
• 24 hour urinary VMA x 3
• MSU x 2 - look for cells, casts, protein
• urinary free cortisol
• renal ultrasound, IVU, renal arteriography
• CXR - look for evidence of end-organ damage

Ambulatory blood pressure monitoring provides an accurate profile of blood pressure fluctuations over a 24 hour period and control for the 'white coat effect'. For example, they may show the paroxysmal rise in blood pressure associated with phaeochromocytoma.