Kidney Function

[ Illustration: Kidney function ]

Over 98 percent of the water and a large portion of the salts and chemicals in this filtrate are reabsorbed by the cells of the kidney tubular system and returned to the blood. In this process of reabsorption, waste chemicals which would be poisonous (toxic) at high concentration in blood, are not reabsorbed and, so, are concentrated in the tubular fluid.

Eventually, a small volume of water and salts with high concentration of waste chemicals is excreted at the end of the tubular system. This fluid, which we know as urine, travels from the kidneys to the bladder through larger tubes called ureters. When the bladder fills with urine, we sense a full bladder and pass urine, thus ridding the body of excess water and waste chemicals. Most people pass between 11/2 and 3 litre of urine each day.

In response to many nerve and chemical signals, the kidneys are able to respond to changes in the behaviour of the individual. If we drink more water, very soon we pass a similar amount of urine. If we ingest excess sodium this is sensed by the body and signals are sent to the kidneys to reabsorb less sodium and, therefore, excrete more sodium in the urine. By such a complex system, and despite the fact that we vary our intake of fluids and foods greatly from day to day, the kidneys maintain an almost constant volume of body water and near constant body water chemistry at all times.

Other important functions provided by the kidneys include:

· Regulation of several hormone systems that are involved in controlling normal blood pressure

· Production of the hormone Erythropoietin, which regulates production of red blood cells and corrects anemia

· The modification of vitamin D in a way that allows normal control of body calcium and regulates bone growth and strength.

The above are intended to be general information and not intended to be treated as a diagnosis whatsoever. You are asked to seek professional medical advice relating to all questions on treatment, care, diagnosis and medication.