The hilum is the kidney’s gateway
Hilum is pronounced high-lum
The recessed part of the kidney is where blood enters and leaves the kidney via arteries and veins, and where waste products (urine) leave via the ureter (see below). This “gateway” is known as the hilum.
When the boy who came off his horse has been cleaned up, he jumps high with his lamb (hilum) over a gateway to show the horse how it’s done.
Diagram of hilum