The hollow or concave side of the kidneys is turned inwards, and the deep fissure of this side, known as the hilus, widens out to form the pelvis.
"A Practical Physiology"
Albert F. Blaisdell
Through the hilus the renal artery passes into each kidney, and from each hilus passes outwards the renal vein, a branch of the inferior vena cava.
"A Practical Physiology"
Albert F. Blaisdell
Notice that all the vessels leave and enter the kidney at the hilus.
"A Practical Physiology"
Albert F. Blaisdell