Paradoxical tubular obstruction after release of ureteral obstruction in rat kidney

The healing process of hydronephrosis was studied using rat kidney. Following release of 2 weeks' unilateral hydronephrosis, renal papilla and cortex were examined by scanning electron microscopy. Shortly after the release of obstruction, massive loss of brush border and ballooning of epithelial cells were noted in proximal tubules. Distal tubules and collecting tubules also showed severe ballooning of epithelial cells. Actually most of them were completely or nearly obliterated in spite of the release of ureteral obstruction. Two weeks later, on the other hand, the many tubular components became patent with normal epithelial lining. Some of them, however, deteriorated further in spite of the release of obstruction. Thus there was a marked tubular heterogenicity in recovery. The sudden decrease of the pelvic pressure and chronic ischemic state during ureteral obstruction may cause the tubular changes which were observed in this study.