The left renal vein is longer than the right renal vein. It is about three times longer and somewhat curved. This is because the left renal vein has to pass over the aorta and the superior mesenteric artery before it enters the inferior vena cava.
The left renal vein also receives blood from the left suprarenal, ovarian, and testicular veins, while the right renal vein only receives blood from the right kidney.
