Renal handling of sodium and water in early chronic liver disease. Evidence for a reduced natriuretic activity of the cirrhotic urinary extracts in rats.

Acute expansion of extracellular fluid volume during maximal water diuresis was induced in 8 chronic liver disease patients without clinical evidence of fluid retention, and in 8 controls. Fractional reabsorption of sodium was inferred in the proximal tubule, in the ascending limb of Henle's loop, and in the more distal site of the tubule. The results indicate that the significantly reduced increment of sodium excretion in cirrhotic patients was due to its augmented reabsorption in the proximal tubule. To establish whether there was a reduced activity of a natriuretic factor, a biologic assay was performed in 16 albino Wistar rats by using urine samples collected immediately after completion of a saline load and processed with gel filtration. The infusion of this fraction resulted in a significant lowering of the increment of urine output, and absolute and fractional sodium excretion only in the rats infused with urine extracts from cirrhotic patients. The results of this study raise the possibility that a reduced production of a natriuretic factor may play some role in the pathogenesis of sodium retention, which is observed in patients with cirrhosis of the liver.