10 Facts about Kidneys


The kidneys are located deep in the lower back to the left and right of the spine near the lower ribs.


Each kidney is shaped like a bean with the size of a fist. It is on average about 11cm long and 6cm wide and 150g in weight. These dimensions are obviously proportional to the person’s height.


The right kidney lies lower than the left kidney as a result of being pushed down by the liver. The right kidney is also slightly smaller than the left.


Most people are born with 2 kidneys but some healthy people can have 1 or 3 or 4 (click here and here to find out more) kidneys too!


The kidneys move up and down by a few centimetres as we breathe in and out.


The kidneys receive 20% of all the blood the heart pumps out. That is just above one thousand millilitres every minute!


Taking in all that blood flow, the kidneys filter out about 120 millilitres of fluid every minute. Don’t worry, they later reabsorb most of the fluid back in the body. After all, we normally pass just over a litre of urine a day!


Each kidney contains just over one million nephrons. A nephron is a miniature filter that receives blood, filters and reabsorbs fluid to produce urine.


Each kidney has a cap above upper pole. This is the adrenal gland which functions separately from the kidney and produces important hormones.


The kidneys shrink slowly as we get older but this process occurs faster and earlier in kidney disease. A badly shrunken kidney will barely function.

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