[Water-, electrolyte- and acid-base equilibrium in the aged].

The functional capacity of the kidney decreases with advancing age. We not only find a reduced glomerular filtration rate but also disturbances in the functioning of the tubules which influence the capacity to dilute and concentrate the urine and the renal electrolyte excretion. In addition, the plasma-renin activity shows decreased response to stimulation; the aldosterone and vasopressin secretions are also decreased in old age. Disturbances of the water-, electrolyte and acid-base equilibrium often cause secondary renal failure. On the other hand, as the renal capacity is limited, renal disorders occurring in old age may lead to quicker decompensation.