The kidneys are bean-shaped organs, each about the size of a tightly clenched fist. They lie on the posterior abdominal wall behind the peritoneum and on either side of the vertebral column near the lateral borders of the psoas muscles. The superior pole of each kidney is protected by the rib cage, and the right kidney is slightly lower than the left because of the presence of the liver superior to it. Each kidney measures about 11 cm long, 5 cm wide, and 3 cm thick and weighs about 130 g. A fibrous connective tissue layer, called the renal capsule, encloses each kidney, and around the renal capsule is a dense deposit of adipose tissue, the renal fat pad, which protects the kidney from mechanical shock. The kidneys and surrounding adipose tissue are anchored to the abdominal wall by a thin layer of connective tissue, the renal fascia.
