Hypotonic urine production and sodium chloride intake in patients with chronic renal failure.

The production of hypotonic urine was investigated in 20 subjects suffering from chronic pyelonephritis. The minimum urinary osmolality was significantly influenced by the NaCl content in the diet. Under conditions of low NaCl intake (15 mEq Na/day) the minimum urinary osmolality decreases significantly as compared with the values obtained under normal salt intake, and can reach normal values. The results indicate that the diluting function of the kidneys may be improved by the increase of fractional sodium reabsorption.