Plasma free metanephrine is 99% specific and 89% sensitive in the diagnosis of pheochromocytoma.1 Once there is strong biochemical evidence of pheochromocytoma, imaging is necessary to define features, such as anatomical relationships, invasion, and multifocality, before surgical intervention can be undertaken. Contrast-enhanced CT and gadolinium-enhanced MRI demonstrate similar sensitivity (90%-100%) and specificity (70%-80%) for pheochromocytoma.2 In a patient with renal insufficiency, MRI is the imaging study of choice because iodinated contrast used with CT is nephrotoxic. Pheochromocytoma typically has high signal intensity on T2-weighted MRI. Fine-needle biopsy of a suspected pheochromocytoma is contraindicated and can cause life-threatening changes in blood pressure.
- MRI of the abdomen and pelvis.
1. Lenders JW, Pacak K, Walther MM, et al. Biochemical diagnosis of pheochromocytoma: which test is best? JAMA 2002;287:1427-34.
2. Lumachi F, Tregnaghi A, Zucchetta P, et al. Sensitivity and positive predictive value of CT, MRI and 123I-MIBG scintigraphy in localizing pheochromocytomas: a prospective study. Nucl Med Commun 2006;27:583-7.
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