A patient with a ruptured abdominal aortic aneurysm underwent an emergency operation. A rare anomaly of inferior vena cava, known as "marsupial cava," was found. The iliac vein confluence crossed anteriorly (rather then posteriorly) the right common iliac artery. Even though the patient had undergone a computed tomography scan, this rare anomaly had not been detected and therefore was unexpected by the surgeon. The aim of this report is to describe the technical details required to perform the aortic reconstruction and to stress the importance of routine computed tomography scans and their careful reading in the case of stable patients before retroperitoneal operation. This is, to our knowledge, the first report of an aortic prosthetic grafting for ruptured aortic aneurysm in association with a marsupial cava.