The function of the kidneys is to filter the blood of toxins, control blood pressure, and excrete urine. They control the amount of water in the body by controlling the amount of sodium in the blood. They also produce a number of hormones, including erythropoietin, which stimulates the bone marrow to make red blood cells.
The kidneys, two small bean-shaped organs that are about 5 inches long, are located on both sides of the spine, below the ribcage. Blood flow through the kidneys normally allows them to excrete wastes, concentrate urine, and conserve electrolytes (mineral salts). Any condition that significantly interferes with blood flow to the kidneys can result in renal failure. Renal failure is a decline in kidney function that occurs either suddenly (acute renal failure) or gradually (chronic renal failure).
The kidneys can be damaged in several ways. The two most common causes of kidney failure are hypertension (high blood pressure) and diabetes. There are several other mechanisms of injury, including atherosclerosis, which occludes the arteries to the kidneys, infection, immunologic factors, and obstruction of the collecting systems.
When the kidney function has diminished to less than 10%, they can no longer support all of the functions the body requires. This means that toxins and fluids can accumulate within the bloodstream. These can approach dangerous levels and become life threatening.
To counteract this, patients can be placed on dialysis, which allows for artificial filtration of the blood. Once committed to dialysis, patients will generally require sessions three times per week to clean the blood. One alternative to dialysis is a kidney transplant, which is a good choice for healthy patients with a matching donor.