[The clonidine inhibition test: an aid in the diagnosis and postoperative therapeutic control in pheochromocytoma].

A clonidine-suppression test was carried out in 8 patients with arterial hypertension, raised urinary and plasma catecholamine levels and symptoms suggesting the presence of a pheochromocytoma. In 6 of the patients clonidine reduced the plasma catecholamine concentrations and no pathological findings were seen in the abdominal computed tomogram (CT). In 2 patients noradrenaline levels were excessively high and not lowered by clonidine; in one of these patients the plasma adrenaline concentration was also raised and this too could not be reduced with clonidine. A tumor was detectable in both patients using CT, in one case situated in the left adrenal, in the other extra-medullary. On operation both were found to be a pheochromocytoma. Peritoneal and intra-hepatic metastases were discovered during surgery in the case of the extramedullary localized tumor. The clonidine-suppression test was repeated postoperatively in both patients: it was normal in the case of the completely excised, intramedullary situated tumor but still pathological in the other. Thus the clonidine-suppression test is useful in the diagnosis and post-surgical assessment of pheochromocytoma.