Right gonadal arteries passing dorsally to the inferior vena cava: embryological hypotheses.

The right gonadal artery (RGA) usually arises from the anterior wall of the abdominal aorta below the level of the renal arteries and veins, passes ventrally to the inferior vena cava (IVC), and then runs obliquely downward to reach the pelvic cavity. In this study, we observed 59 Japanese cadavers and found that in eight of them (13.6%), the RGA's passed dorsally to the IVC. Together with the various courses of RGAs reported in the literature, we here divided the courses into four subtypes, due to the relationship to the left renal vein and the IVC, of superior, middle and lower types (L1 = ventrally, L2 = dorsal of IVC). Superior type was seen in 3.6%. Lower types were fount to in the most cases (L1: 83.5%, L2: 13.6%). The middle type was not realized. The classification of this variations make it easy to describe the RGA's passing below the level of the left renal vein. RGA can pass either ventrally or dorsally to the IVC. RGAs passing at or above the level of the left renal vein run dorsally but not ventrally to the IVC. The variations in the origin, course and branching of RGAs are attributed to development of the IVC.