PHEOCHROMOCYTOMA - EFFECT OF NONIONIC CONTRAST-MEDIUM IN CT ON CIRCULATING CATECHOLAMINE LEVELS

PURPOSE: To study the catecholamine-releasing effect of peripheral int ravenous administration of the nonionic contrast medium iohexol in pat ients with pheochromocytomas. MATERIALS AND METHODS: Ten patients (eig ht women, two men; mean age, 44 years; age range, 25-70 years) with ph eochromocytomas and related tumors and six healthy volunteers (five me n, one woman; mean age, 31 years; age range, 27-35 years) were examine d Plasma catecholamine levels were measured at intervals for 60 minute s after the injection of 0.9% saline or iohexol on 2 separate days. Al l 10 patients intravenously received the specific alpha-adrenergic blo cker phenoxybenzamine hydrochloride (0.5 mg/kg in 250 mt of 5% dextros e infused over 2 hours) 24 hours before iohexol-enhanced computed tomo graphy. RESULTS: There was no statistically significant increase in ep inephrine or norepinephrine levels in the patients or the control subj ects. CONCLUSION: While it may be prudent to administer oral alpha- an d beta-adrenoceptor antagonists in all patients with a biochemically p roved pheochromocytoma to control their symptoms and to prevent a spon taneous adrenergic crisis, specific blockade may not be required befor e contrast medium-enhanced scanning with iohexol. Although the sample size of this study is relatively small, the results do suggest that in an incidentally detected, clinically silent adrenal mass that may or may not be hypersecreting, the nonionic contrast medium iohexol may be used for scanning without blockade.