Impaired renal water excretion in liver cirrhosis. The role of reduced distal delivery of sodium.

The study was aimed to assess the relationships between distal sodium delivery and renal diluting ability in liver cirrhosis. Renal response to maximal water load was evaluated in 18 cirrhotic patients without ascites, 12 with mild or moderate ascites, and 26 controls. Distal sodium delivery was derived from clearance calculations during the hypotonic diuresis induced by maximal water load. Although ascitic patients showed a greater impairment in free-water excretion, the pattern of the renal response to maximal water load was similar in ascitic and non-ascitic patients; it was characterized by reduced free-water clearance and reduced distal delivery of sodium. Free-water clearance corrected for distal sodium delivery was normal in non-ascitic patients and in the majority (75%) of decompensated cirrhotics, indicating a primary role of an increased proximal sodium resorption in the pathogenesis of the impaired water excretion of these patients. Renal diluting capacity did not correlate with the severity of liver functional impairment, as evaluated by single liver function tests or by Child's criteria