The human body has two kidneys, left and right, each of which is located on both sides of the lumbar and retroperitoneal spine. The kidney shape such as beans, edge uplift, inner middle sag, about the size of two fists. Each kidney is about 9~12 cm long, 5~6 cm wide, 3~4 cm thick and 120~150 grams heavy. The shape, size, and weight of the two kidneys were approximately similar. The left kidney was slightly larger than the right kidney. Normally, the bilateral kidneys are not exactly the same size. As long as it is physiological and the renal function is normal, it does not matter. The main structure and function of the kidney include:

1. glomerulus: complete renal filtration, removal of metabolites and toxins in the body.

2. the renal tubular: re absorption useful substances in the glomerular filtrate (sugar, amino acids, small proteins and minerals), local secretion of some regulating factors, remove some metabolites and excretion of drugs, regulation of acid-base balance and water.

3. collecting tubes and the renal pelvis: the urinary drainage line, which is involved in the regulation of water balance.

The renal excretion of metabolic waste and excess water and potassium, sodium, chlorine, hydrogen ions through the electrolyte to produce urine to excrete waste and poison, regulating water, electrolyte and acid-base balance, maintain homeostasis function; kidney filtration and cleaning every day about 200 liters of blood - number the equivalent of 10 barrels of drinking water! The kidney is the important endocrine function, can produce vasoactive substances such as renin, prostaglandins, kallikrein and bradykinin, regulating blood pressure and blood pressure to maintain a relatively stable; can produce erythropoietin and active vitamin D3 to promote bone marrow and regulating the metabolism of calcium and phosphorus.