Factors influencing the severity and progress of ethylenimine-induced papillary necrosis.

The severity of the renal papillary necrosis produced in rats by ethylenimine is dependent both on dose and urinary concentration within the medulla. When this is reduced by diuresis, the severity of the lesion is effectively reduced. Increasing urinary concentration has a reverse effect, but of less magnitude. When the concentrating power of the renal medulla is impaired by a single dose of ethylenimine, insufficient to cause necrosis of the whole papilla, further doses of ethylenimine do not cause progressive damage to the papilla.