One of the two bean-shaped organs located on each side of the spine in the retroperitoneum. The right kidney is located below the liver and the left kidney below the diaphragm. The kidneys filter and secret the metabolic products and minerals from the blood, thus maintaining the homeostasis. On the superior pole of each kidney there is an adrenal gland. Each kidney and adrenal gland is surrounded by fat [National Cancer Institute Thesaurus].