The ratio of the blood urea nitrogen/creatinine index in patients with acute renal failure is decreased due to dextran or mannitol.

Acute renal failure (ARF) induced by dextran or mannitol is a lethal adverse effect, and hemodialysis or plasma exchange is recommended to avoid fatal ARF. This report describes 2 cases of ARF; one caused by dextran and the other by mannitol. Both showed decreases in the blood urea nitrogen (BUN)/creatinine ratios after the administration of these reagents. They immediately recovered to the level of creatinine on admission after the administration of these reagents was stopped, without hemodialysis or plasma exchange. Decreases in the BUN/creatinine ratio might be a useful index for the diagnosis of ARF is caused by these reagents.