Most clinicians rely on the clinical history of the patient to suggest the diagnosis and do not routinely measure catecholamines in all patients with hypertension. In a patient suspected of having a phaeochromocytoma, the first investigative step is to measure the urinary excretion of vanillylmandelic acid (VMA); the excretion is elevated in ninety per cent of patients with phaeochromocytomas. Occasionally, however, the level of VMA is normal. In such instances, metanephrines should be measured in the urine; alternatively, and more reliably, plasma and urinary levels of adrenaline and noradrenaline should be measured.
