A new test to predict reversibility of hydronephrotic atrophy after stable partial unilateral ureteral obstruction

In previous studies we showed that hydronephrotic atrophy develops only in the first weeks after stable partial ureteral obstruction, and does not progress thereafter. Relief of obstruction only in the "destructive phase" and not in the later "steady-state phase" seems to improve or prevent hydronephrotic atrophy. Since the duration of partial ureteral obstruction is often not known, we studied urinary enzymes of rat kidneys after stable partial unilateral ureteral obstruction to identify the destructive phase. We chose as an example of the tubular lysosomal enzyme N-acetyl glucosaminidase (NAG) and as an example of the brush border enzyme gamma-glutamyl-transferase (Gamma-GT). NAG concentration but not so much Gamma-GT concentration was higher in the urine of the obstructed kidneys than in the urine of the contralateral control kidney, in the first two weeks after operation, and then returned to normal. These observations lead to the conclusion that the "destructive phase" after ureteral obstruction can be identified by the appearance of high urinary tubular lysosomal enzyme content. The clinical implication is that the timing of relief of asymptomatic stable partial ureteral obstruction of unknown duration can be based on the concentrations of urinary lysosomal enzymes.