Renal sodium retention in cirrhosis: Tubular site and relation to hepatic dysfunction

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Abstract
Renal sodium handling, assessed by the response to acute saline loading, was investigated in 14 well-compensated, nonascitic alcoholic cirrhotics and six normal controls. Urinary sodium excretion in cirrhotic patients (199 ± 141 μmoles per min) was significantly lower than in controls (387 ± 104 μmoles per min; p < 0.01) at 3 hr postinfusion. In contrast to controls, renal plasma flow and glomerular filtration rate did not increase in the cirrhotics in response to acute saline loading. Proximal fractional reabsorption of sodium was estimated by clearance techniques in the presence of a hypotonic diuresis. Cirrhotic subjects with impaired functional liver cell mass as assessed by antipyrine clearance were unable to decrease proximal fractional reabsorption of sodium significantly in response to saline loading. Assessment in the cirrhotics included measurement of hepatic vein pressure gradient, indocyanine green extraction ratio, indocyanine green clearance, and antipyrine clearance as indices of portal pressure, intrahepatic shunting, hepatic blood flow and functional hepatocellular mass, respectively. Urinary sodium excretion in the cirrhotics correlated strongly with antipyrine clearance (r = 0.839, p < 0.0001) and weakly with portal pressure (r = 0.562, p = 0.037). No correlation was seen with the other indices of hepatic blood flow and shunting. The findings of this study suggest that alcoholic cirrhosis is associated with a decline in hepatocellular function which results in either a decreased clearance of a salt-retaining hormone or decreased synthesis of a natriuretic hormone. This hormone has as its principal effect the modulation of renal afferent vasomotor tone such that, in cirrhotics, renal plasma flow, glomerular filtration rate and proximal tubular sodium reabsorption cannot be altered in response to a salt load. Release of this hormone may be influenced by the degree of sinusoidal hypertension or hepatic venous outflow resistance.