Malfunctioning of the kidney

The kidneys, apart from excreting waste materials from the body, play a very important role in maintaining the water and salt content of the blood, and hence the tissue fluids and cell contents at a constant level. The absorption of water by the collecting duct is influenced by the hormone ADH (anti-diuretic hormone) produced by the pituitary gland. When the amount of water in the body is low, as the body begins to be dehydrated, the concentration of salts in the blood increases. This results in an increase in the osmotic concentration of the blood. The brain detects this change and nerve impulses to the pituitary gland stimulate increased amounts of ADH. This increases the permeability of cells of the collecting ducts and they reabsorb more water. This normalises the water content of the blood. If, one the other hand, the water content of the blood increases considerably, a decrease in the osmotic pressure of the blood results. Less ADH is released, the collecting ducts absorb less water, and large amounts of dilute urine are then produced. A close examination of the constituents of urine is important in diagnosing certain disorders in the body. If on analysing urine it is found to contain glucose, the disease called diabetes mellitus is evident. Occasionally, when people are unable to secrete sufficient ADH, they tend to excrete large amounts of urine. They sufferer therefore tends to drink enormous quantities of water to replace the loss in urine. This condition is known as diabetes insipidus. This can be remedied by regular nasal spraying with ADH. Another disease which the analysis of urine can give an indication of is nephritis. This afflicts people when the glomeruli become faulty and allow protein to filter through into the glomerular filtrate, ultimately appearing in the urine. Occasionally people may suffer from kidney failure, this might happen suddenly due to severe infection or low blood pressure, or gradually as a result of high blood pressure. It is possible to live with one kidney only, but it is fatal when both fail. Partial kidney failure can be treated by controlled diet, by dialysis using a kidney machine, by kidney transplant.