What Are Kidneys?

Human kidneys are bean-shaped organs located near the middle of the back on both sides where they are protected by lower ribs and cushioned by the surrounding muscles and fat. Each kidney is about the size of a clenched fist and weighs about 150 grams. Each kidney has about one million nephrons, which are tiny, filtering units. In the nephrons, capillaries or tiny blood vessels intertwine with tubules, which are urine-carrying tubes. The nephrons make it possible for the kidneys to filter the body’s entire blood supply. 


What Do Kidneys Do?

Kidneys mainly process the waste products and excess fluid in your blood. The waste products result from our body’s metabolic processes. In addition, waste is also a by-product of the food we eat. Our body uses food for energy and self-repair. After it has absorbed what it needs from the food, the remaining waste products are sent to the blood.

A complicated chemical exchange takes place as the blood is filtered by the nephrons. The filtering process removes the waste, toxins and excess water from the blood to form urine. Urine flows from the kidneys to the ureters and then stored in the bladder until we urinate. In addition, the kidneys regulate the chemical balance in our body.

They release three important hormones:

  • Erythropoietin (pronounced eh-RITH-ro-Poyeh-tin) aids in red blood cell formation
  • Renin (pronounced REE-nin) maintains a normal blood pressure
  • The active form of Vitamin D, which helps keep our bones strong

What is Kidney Failure?


Kidney failure or End-Stage Renal Disease (ESRD) is defined as a state when the kidneys do not function properly or sufficiently, resulting in the accumulation of waste products and toxic materials.

When toxic wastes build in the blood, they may cause permanent and irreversible damage to body cells, tissues and organs. Thus, in order to survive, kidney function needs to be replaced either through dialysis or transplant.

A person can stay healthy with just one kidney. Individuals with kidneys that function below 20% of their required capacity, however, need some form of renal replacement therapy.