Late return of renal function after correction of chronic obstruction

A 57-year-old man presented with renal failure secondary to bilateral interstitial nephritis and left hydronephrosis owing to a calculus in the renal pelvis, creatinine clearance being 2.4 cc per minute. Renal function did not improve after left pyelolithotomy and hemodialysis was instituted. No demonstrable change in renal function could be detected until 10 weeks postoperatively when creatinine clearance was 25 cc per minute.