A urinary sodium concentration [U(Na)] of less than 10 mmoles per liter is considered important in differentiating hepatorenal syndrome from other causes of progressive renal impairment in patients with liver disease. However, occasionally, patients with hepatorenal syndrome have been recognized in whom the U(Na) is consistently greater than 10 mmoles per liter. Eight such patients, in all of whom there was no clinical or laboratory evidence to implicate other causes of progressive renal impairment, were identified. The clinical features, hepatic and renal status and hospital course were compared with eight other patients who had hepatorenal syndrome and a U(Na) consistently less than 10 mmoles per liter. The mean U(Na) was 24 +/- 4 mmoles per liter in the high U(Na) group and 3.7 +/- 1.8 mmoles per liter in the low U(Na) group. All patients in both groups had acutely decompensated alcoholic hepatitis of similar severity and activity. The high U(Na) group had significantly less clinical ascites and peripheral edema and higher serum levels of sodium and chloride both at the onset of the hepatorenal syndrome and throughout the clinical course. Significant differences in the serum potassium and blood urea nitrogen levels became apparent between the two groups of patients as renal failure progressed, and the mean average blood urea nitrogen to serum creatinine ratio was significantly higher (p less than 0.025) in the low U(Na) group (13.8 +/- 0.9 vs. 10.1 +/- 1.1). Mean urinary potassium concentration was significantly higher in the high U(Na) patients but urinary creatinine concentrations, specific gravity and sediment were similar in both groups of patients.(ABSTRACT TRUNCATED AT 250 WORDS)