[Pheochromocytoma in internal medicine: distinctive features and place of 123I MIBG scintigraphy].

PURPOSE: Pheochromocytoma diagnosis uses the localization of the tumour, particularly thanks to MIBG scintigraphy. The aims of this study were to evaluate the sensibility and specificity of this exam, his opportunity towards clinical and biological profile of patients with pheochromocytoma suspicion in Internal Medicine and towards others techniques of imaging. We tried to define the most effective and least expensive approach of pheochromocytoma diagnosis.

METHOD: This study was carried out over 15 years period on 80 patients in Internal Medicine who underwent 123I MIBG scintigraphy for pheochromocytoma suspicion.

RESULTS: Among the 80 patients who underwent 123I MIBG scintigraphy, only 18 suffered from a pheochromocytoma. A very few symptoms were specific, like the triad "headaches, sweating, palpitations" whose onlyone third of patients was concerned by. The diagnosis approach carried on with urine catecholamine measurement, who was specific when metanephrines were increased whatever their levels and when normetanephrines were higher or equal than 1,5 time the norme. Then, abdominal CT or MRI scanning and 123I MIBG scintigraphy were performed for localization of the tumor. The sensibility of scintigraphy was 83%, its specificity was 89%. That is comparable with other studies about 131I MIBG.

CONCLUSION: Prescription of MIBG scintigraphy in Internal Medicine appears to be excessive: 77,5% of patients don't have a pheochromocytoma. It is related to the lack of specific symptoms, the wrong positives in urine normetanephrines measurement and the discovery of incidentaloms by CT scanning. The scintigraphy should be used like a topographic and not a diagnosis exam.