Recognize the clinical presentation and differential diagnosis of acute renal failure in a patient with liver disease and low fractional excretion of sodium

Explanation

Most cases of oliguria in any hospitalized patient would be pre-renal. Pre renal failure of kidneys tries to conserve fluid and the Fractional excretion of sodium (FENa) is low. The only other conditions with low FENa where one is likely to be tested is Hepatorenal Syndrome, rhabdomyolysis and contrast nephropathy. These can be distinguished on the basis of Wedge pressure.

In Pre renal failure the wedge is low while in Hepatorenal syndrome, rhabdomyolysis and contrast nephropathy it is normal (and a fluid challenge does not improve the urine output).

Precipitants of hepatorenal are infection, diuretics, GI bleed or Paracentesis.

If you are going into renal fellowship you should know that the levels of endothelin in hepatorenal syndrome are elevated and may be responsible for the vascular shunting.