A variety of methods have been used to locate phaeochromoctomas. Eighty-five to ninety per cent of these tumours arise from the adrenal medulla, and in ten per cent of cases, the tumours are bilateral. Non-adrenal tumours may arise from sympathetic ganglia, usual: alongside the aorta or its branches or, rarely, in the wall of the urinary bladder. Less than one per cent of phaeochromocytomas are found outside the abdominal cavity. In patients in whom a phaeochromocytoma cannot be localised by CT, nuclear scanning or arteriography, it may be necessary to perform a venous catheter study and measure catecholamine levels in all the major veins to determine the source of catecholamine excess.
