Extra-adrenal retroperitoneal paraganglioma associated with duplication of inferior vena cava.

Retroperitoneal paragangliomas arise from specialized neural crest cells symmetrically distributed along the aorta in association with the sympathetic chain. If this tissue aggregates in the adrenal medulla pheochromocytoma may arise. When it remains in the paraaortic sites it could develop into extra-adrenal, retroperitoneal paraganglioma. We report a case of extra-adrenal paraganglioma in the renal hilum intimately related to the left side of a double inferior vena cava. To the best of our knowledge such an association has never been described before. The clinical significance of this venous anomaly is reviewed.