Kidney Physiology

The kidneys are vital organs responsible for clearing waste products, salts and water from the body. Each person has two kidneys located on either side of the lower back. They are about the size of a human fist and filter about 200qts of fluid every 24 hours. When your kidneys aren’t functioning the way they should be, these waste products start to build up and are not cleared from the body. Symptoms of disease typically don’t start to appear until kidney function is reduced to less than 15%.

The main functions of kidneys are:

  • Excretion of wastes: kidneys excrete urea and uric acid into the urine, which are products of metabolism.
  • Reabsorption of vital nutrients, which includes: glucose (at normal plasma level), amino acids, water, sodium, chloride, potassium, magnesium, calcium, bicarbonate and phosphate.
  • Acid-Base homeostasis: which is maintenance of balance between chemical acids and bases, also called body PH.
  • Maintenance of Electrolyte-Water balance: which is called plasma osmolarity.
  • Hormone secretion: kidneys secrete Erythropoietin (regulates the production of red blood cells in bone marrow), Renin (controls blood pressure) and Calcitriol (active form of vitamin D makes bone stay strong).

Disclaimer: The UCLA Health System cannot guarantee the accuracy of such information. The information is provided without warranty or guarantee of any kind. Please speak to your Physician before making any changes.