Extra-adrenal pheochromocytoma: an unusual location.

A 14-year-old boy with a retrohepatic para-aortic pheochromocytoma demonstrates the potential difficulties of localization in an unusual extra-adrenal site of pheochromocytoma. Ultrasonography, computed tomography, metaiodobenzylguanidine scanning, and angiography with venous sampling failed to define the true anatomic location of this tumor. Collateral venous drainage produced confusing venous sampling data and represents a potential pitfall in the interpretation of these studies.