The kidneys filter blood and remove wastes that are then transported through the ureters to the urinary_bladder. The bladder empties its contents through the urethra. The urethra of the male has a dual function. It carries urine as well as reproductive fluids (but not at the same time). The urethra of a female has only one function - urinary excretion. In humans, one adrenal_gland sits on top of each kidney; hence they are said to be suprarenal. In cats, however, the adrenals are separate from the kidneys and are embedded in mesentery.

The outer surface of the kidney is covered with a CT capsule, and has an indented region known as the hilus where blood vessels and a ureter connect to the kidney.