RENAL HISTOLOGY IN URETEROPELVIC JUNCTION OBSTRUCTION - ARE HISTOLOGICAL-CHANGES A CONSEQUENCE OF HYPERFILTRATION

Purpose: There are few reports of pathological kidney findings in uret eropelvic junction obstruction in pediatric patients. The role of hype rfiltration in the genesis and progression of these changes has been a matter of debate. We determine whether segmental sclerosis is evidenc e of hyperfiltration and renal damage in children who underwent surger y for ureteropelvic junction obstruction. Materials and Methods: We re trospectively analyzed the clinical records of 38 children with a mean age of 4.4 years with ureteropelvic junction obstruction. Histologica l changes in biopsies (39 renal units) and nephrectomy specimens (2 re nal units) were compared with clinical history, imaging studies and ur inary protein excretion. Results: Renal histology was essentially norm al in 75% of the biopsies. Focal dilatation of Bowman's space and occa sionally of the collecting tubules was noted in a third of this group. Abnormal changes consistent with renal damage were present in 25% of the biopsies, including variable degrees of interstitial chronic infla mmation, eosinophilic acellular material within Bowman's space and foc al concentric glomerulosclerosis. Severe changes, chronic interstitial fibrosis and inflammation, and diffuse glomerulosclerosis were only f ound in nephrectomy specimens, while eosinophilic acellular material a nd glomerulosclerosis were observed in 7 biopsies; In all of these ren al units there was evidence of hyperfiltration with bilateral or unila teral ureteropelvic junction obstruction with a contralateral multicys tic dysplastic kidney. Urinary protein excretion in 19 patients was in creased in obstructed compared with normal contralateral kidneys (p <0 .05). Conclusions: Hyperfiltration should be considered a mechanism in volved in the progression of histological changes in kidneys with uret eropelvic junction obstruction. We suggest that early surgical correct ion be considered in obstructed kidneys at risk for hyperfiltration.