Interstitial nephritis associated with perianeurysmal retroperitoneal fibrosis.

Renal failure in retroperitoneal fibrosis is usually secondary to ureteric obstruction. We report a patient whose renal failure did not improve following relief of obstruction. Renal biopsy showed an interstitial nephritis, and function improved with steroid therapy. We suggest that renal biopsy should be considered in cases of renal failure associated with retroperitoneal fibrosis that do not respond to the relief of ureteric obstruction.