The main function of the kidneys is to filter waste from the blood supply which we then secrete as urine. They do this with the help of nephrons which are fine tube like filters which the blood passes through leaving waste products behind. This waste then travels through the nephrons, into the uterer and then into the bladder where it is then expelled out of the system as urine. Kidney stones can get in the way of this process and make it harder for the waste removal.

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