To the Editor.
—The inadequacy of the fractional excretion of sodium test for differentiating causes of oliguria after radiographic contrast infusion as pointed out by Fang et al in the April Archives (1980;140:531-533) has important clinical implications. Fluid volume challenges for presumed dehydration may be hazardous to the patient with established renal tubular injury. The following case report confirms the observations of Fang et al.
Report of a Case.
—A 63-year-old man was admitted to the hospital for examination of an abdominal mass. He was taking no nephrotoxic drugs and was given no enemas, purgatives, or diuretics before angiography. The baseline BUN and serum creatinine levels were 27 mg/dL and 1.0 mg/ dL, respectively. The patient received fluids by mouth or intravenously throughout the entire preangiography and postangiography period. The baseline serum sodium level (139 mEq/L) fell to 135 mEq/L on the first postangiography day, probably reflecting volume expansion consequent