I131 MIBG imaging in the diagnosis of pheochromocytoma: Philippine setting

ABSTRACT

The clinical diagnosis of pheochromocytoma is easy, considering that it manifests as labile hypertension, attacks of palpitations, headache, sweating, pallor or flushing. Urinary VMA or metanephrines seem to be the first investigative step as well as a CT scan to localize it as 85-90 percent arise from the adrenal medulla. Ten percent of these tumors are bilateral but non-adrenal tumors may arise from the sympathetic ganglia, usually alongside the aorta or its branches and in the wall of the urinary bladder. One percent is found outside the abdominal cavity. Meta-iodobenzyl guanidine (MIBG) is an excellent scanning agent that is taken up by most benign and malignant pheochromocytoma tissues. While this procedure is quite costly and underutilized in the Philippines, this paper was done to review its indications and how helpful it can be. From 2001 -2005, I131 MIBG scintigraphy was done only in 17 patients in two medical centers to confirm the diagnosis of pheochromocytoma. The clinicians must be informed that this is not a screening procedure but it is particularly helpful in surveying the entire body for adrenal and extra-adrenal metastatic lesions. It is also diagnostic of intra-adrenal paragangliomas, neuroblastoma, carcinoids, and medullary thyroid carcinoma. This study was, likewise, done with the thought that MIBG may be utilized in the future for therapy as it has shown to be effective in pheochromocytoma and neuroblastoma.