Urinary Dilution in Potassium Deficiency ‡

One of the earliest manifestations of potassium depletion is a reduction in the ability of the kidneys to elaborate a concentrated urine.' This defect has been shown to result at least in part from a decrease in the concentration of sodium in the interstitial fluids of the renal medulla and papilla.9 The disturbance in renal concentrating ability may exist without impairment of glomerular filtration rate; renal extraction of para-aminohippurate'0 and the ability of the kidneys to excrete a highly acid urine, however, are frequently deficient.' The present experiments have explored the ability of potassium-deficient animals to excrete a dilute urine in response to a water load. In contrast to certain other diseases of the kidney accompanied by hyposthenuria, the kidneys of potassium-depleted animals appear to dilute the urine normally. Studies of urinary dilution and concentration in two patients with severe potassium deficiency are also reported.