ABSTRACT
The four main functions are: • elimination of waste products; • maintenance of water and electrolyte balance, in particular the balance of
sodium and potassium in the body; • maintenance of acid base balance, ie the balance between the concentration
of hydrogen ions taken in and eliminated; and • production of hormones and enzymes. The most important natural waste products of body metabolism contain nitrogen and are products of the food containing protein ingested, and breakdown of body protein, for example from muscle. Such breakdown of protein (catabolism) and build-up of protein (anabolism) is occurring continuously in life. The most important toxic nitrogenous waste products retained in kidney failure have not been defined. Two that are measurable in blood and other fluids are urea and creatinine. The latter is derived largely from muscle. Although not particularly toxic in themselves, it is hoped and believed by nephrologists that the concentration of these substances in blood reflect reasonably accurately the concentration of more important nitrogenous waste products as yet unidentified.
