Kidneys

The kidneys are two bean-shaped organs located near the back of the abdomen, one on each side of the spine. Their main role is to filter the blood and remove excess water, salts and waste products, which are eliminated from the body as urine. Each kidney contains about one million tiny filtering units called nephrons.

As blood passes through these structures, useful substances such as most water, glucose and many minerals are reabsorbed, while unwanted substances remain in the forming urine. The urine then flows through the ureters to the bladder, where it is stored before leaving the body through the urethra. Besides producing urine, the kidneys play a vital role in maintaining the body's internal balance.

They help regulate blood pressure by releasing hormones that influence the circulatory system, maintain the proper balance of water, electrolytes and acidity, and produce erythropoietin, a hormone that stimulates the formation of red blood cells in the bone marrow. They also activate vitamin D, which is essential for healthy bones and normal calcium absorption.

Healthy kidneys usually perform these tasks continuously without conscious effort. Drinking enough water, avoiding tobacco, controlling blood pressure and diabetes, and limiting excessive use of certain medications all help protect kidney function. Blood and urine tests can detect many kidney disorders at an early stage.