normally, the ovarian vein crosses over the ureter at the level of the fourth or fifth lumbar vertebral bone. the ureter itself courses over the external iliac artery and vein. thus, these vessels can impinge on the ureter causing obstruction. the left ovarian vein ends in the renal vein whereas the right ovarian vein normally enters into the inferior vena cava. in the case of right ovarian vein syndrome, the vein often ends in the renal vein. this is thought to contribute to venous engorgement, in analogy to what is seen in varicoceles, which arise more commonly on the left side. the straight angle between the ovarian vein (or testicular vein in males in the case of varicocoele) and the renal vein has been proposed as a cause of decreased blood return.