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Information > Kidney Disease > About the kidneys

What and where are the kidneys?

The two kidneys – the renal organs – are the master chemists of the body. They monitor the quality of the blood, separating harmful substances from the beneficial ones, acting not only as waste disposal units but also like sophisticated sieves retrieving useful substances that slip through the holes. The kidneys maintain the internal environment essential for life – whatever the diet or the climate.

The kidneys filter the blood, clean it and keep its composition balanced. They maintain appropriate levels of fluids, minerals and other substances including salt and water. They react to hormones from the brain and produce vital hormones of their own.

We can live quite well with only one kidney – indeed, some people live healthily even though born with one missing. But while bones can break, muscles can waste away and the brain can sleep without risk to life, if both kidneys fail – renal failure – neither bone nor muscle nor brain can carry on. Instead, wastes and fluids will build up and poison our whole system.


The kidneys are bean-shaped organs about the size of a fist. They are located at the bottom of the rib cage at the back of the body.

What do the kidneys do?

Healthy kidneys filter the blood to

• remove waste products (from metabolism of the food we eat and body cells).

• remove excess fluid to balance fluid levels in the body


In addition to filtering the blood, the kidneys also:

• help control blood pressure

• produce hormones and chemicals which

• help production of red blood cells

• maintain healthy bones

  • How do the kidneys work

The Kidneys act like sieves, filtering the waste and excess fluid from the blood. Blood passes through the kidneys and is cleaned before returning to the heart. First blood enters the kidneys via the renal arteries. Then, inside the kidneys, millions of mini-filtering systems called nephrons sieve the blood.Certain substances the body needs are reabsorbed and the waste products and extra fluid that the body doesn’t need are removed in the form of urine.The bladder stores the urine until it is full, when the urine passes out of the body via the urethra.

Each day, the kidneys process about 190 litres of blood through 225km of “tubes” and millions of mini filtering systems called “nephrons”. In addition to filtering the blood and balancing fluid levels in the body, the kidneys also produce different hormones and chemicals, which perform several key functions.

Erythropoietin is a hormone which travels in the bloodstream from the kidneys to the bone marrow where it prompts the bone marrow to make red blood cells.  Red blood cells carry the oxygen the body needs to function properly. Without healthy red blood cells, people develop anaemia, which can cause them to feel weak, cold, tired and short of breath. Dialysis does not replace this important function of the kidney.

When kidneys are diseased, blood pressure increases it is important that this is controlled. High blood pressure is a concern it can increase the risk of stroke, heart disease and further damage the kidneys. For the bones to be strong, the kidneys must be able to maintain a healthy balance of substances – calcium, phosphate and vitamin d in the body. Kidney Failure result in abnormal levels of these substances and lead to Renal Bone Disease.

ESKD is a complete or near complete irreversible failure of the kidneys to function to excrete wastes, concentrates urine, and regulates electrolytes. ESKD occurs when the kidneys are no longer able to function at a level that is necessary for day-to-day life. It usually occurs as chronic renal failure worsens to the point where kidney function is less than 10% of normal. At this point, the kidney function is so poor that without dialysis or kidney transplantation, complications are multiple and severe, and death will occur from accumulation of fluids and waste products in the body.


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