Filtering the blood

The kidnevs remove wastes and excess water (fluid) collected bv. and carried in. the blood as it flows through the bodv.

About 190 litres of blood enter the kidnevs every dav via the renal arteries. Millions of tinv filters inside the kidnevs separate wastes and water from the blood. Most of these unwanted substances come from what we eat and drink. The kidnevs automatically remove the right amount of salt and other minerals from the blood to leave iust the quantities the bodv needs.

The cleansed blood returns to the heart and recirculates through the bodv. Excess wastes and fluid leave the kidnevs in the form of urine. Urine is stored in the bladder until it is frill and then leaves the bodv via the urethra. Most people pass about 2 litres of urine every dav

Balancing fluid levels

Bv removing iust the right amount of excess fluid, healthv kidneys maintain what is called the body's fluid balance.

In women, fluid content stavs Ы about 55% of total weight. In men. it stavs at about 60% of total weight. The kidnevs maintain these proportions bv balancing the amount of fluid that leaves the bodv against the amount entering the bodv.

Fluid comes into our bodies from what we drink, and from high-liauid foods such as soup. If we drink a lot. healthv kidnevs remove the excess fluid and we pass a lot of urine. If we don't drink much, the kidnevs retain fluid and we don't oass much urine.

Fluid also leaves the bodv through sweat, breath, and faeces. If the weather is hot and we lose a lot of fluid bv sweating, then the kidnevs will not oass so much urine. As vour kidnevs fail, maintaining this balance becomes more difficult. You mav suffer svmotoms of loo much fluid. You mav need to watch vour diet and what vou drink to maintain fluid balance.