Chronic renal disease defined as a glomerulus filtration rate of less than 60ml/min for at least three months, often develops silently and insidiously over many years. Filtrate formation decreases gradually, nitrogenous wastes accumulate in the blood, and the blood pH drift toward the acidic range. The leading cause of chronic renal disease is diabetes mellitus, with hypertension a close second. Other causes include repeated kidney infection, physical trauma, and chemical poisoning by heavy metals.
In renal failure (GFR<15ml/min), filtrate formation decreases or stops completely. Ionic and pH imbalances build up and wastes accumulate quickly in the blood. At this point, the treatment options are hemodyalisis or a kidney transplant. Hemodyalisis uses an “artificial kidney” apparatus, passing the patient’s blood through a membran tubing that is permeable only to selected substances. The tubing is immersed in a bathing solution that differs slightly from normal cleansed plasma. As blood circulates through the tubing, substances such as nitrogenous wastes and K+ present in the blood (but not in the bath) diffuse out of the blood into the surrounding solution, and substances to be added to the blood, mainly buffers for H+ (and glucose for malnourished patients), move from the bathing solution into the blood. In this way, needed substances are retained in the blood or added to it, while wastes and ion excesses are removed,