Compensatory uptake of I-123 MIBG in the contralateral adrenal gland after removal of a pheochromocytoma.

The identification of recurrent or residual tumor tissue is sometimes complicated. The authors describe a 53-year-old woman in whom I-123 metaiodobenzylguanidine (MIBG) scintigraphy revealed a pheochromocytoma in the right adrenal gland. After the tumor was removed, the patient's catecholamine levels normalized. At the 3-month follow-up examination, I-123 MIBG scintigraphy did not reveal uptake in the right adrenal region but rather showed uptake in the left adrenal region. The patient's blood pressure remained in the normal range. A third scintigram, obtained 1 year after tumor resection, no longer detected I-123 MIBG accumulation in the left adrenal gland. These findings suggest that compensatory hyperplasia of the left adrenal gland led to enhanced uptake of I-123 MIBG. They also highlight the need for careful follow-up of such patients to distinguish between physiologic and pathologic processes.