Internal Medicine Shelf Exam Practice Test 2026 – Complete Study Resource

The most appropriate imaging modality for diagnosing pheochromocytoma is the MIBG (metaiodobenzylguanidine) scan. This imaging technique is particularly effective because pheochromocytomas are catecholamine-secreting tumors derived from the adrenal medulla, and they can take up MIBG due to their neural crest origin. The uptake of MIBG in these tumors allows for clear visualization and confirmation of the presence of a pheochromocytoma.

While CT scans and MRI can also be employed to identify adrenal tumors and assess their morphology, they do not have the same level of specificity for pheochromocytomas as MIBG scans. CT scans are often used as a first-line imaging tool to evaluate adrenal masses, but they do not definitively confirm the diagnosis of pheochromocytoma. Ultrasound is generally not considered a reliable modality for this purpose, as it has limitations in visualizing the adrenal glands and distinguishing adrenal masses. Thus, the MIBG scan stands out as the preferred method for confirming pheochromocytoma due to its ability to functionally image the tumor based on its biochemical activity.