Renal biopsy in congenital ureteropelvic junction obstruction: Evidence for parenchymal maldevelopment

The renal histologic changes associated with congenital ureteropelvic junction obstruction (UPJO) and the relationship to clinical imaging have not been well studied. In order to better understand the histologic alterations of congenital UPJO and their relationship with clinical imaging and outcomes, we examined renal biopsies from 61 patients undergoing pyeloplasty for congenital UPJO. Glomeruli were analyzed for various injury patterns and the tubulointerstitium was examined for tubular atrophy/simplification and fibrosis. Two methods were used to evaluate tubular mass: glomerular density and morphometric measurement of tubular size and density. Control specimens were obtained from age-matched autopsy specimens without renal pathology. Glomerular changes were identified in 73% of all biopsies and were present in a range from 1.7 to 91% of glomeruli in each patient. Overt tubulointerstitial changes were present in 26% of all biopsies. Fibrosis was noted to occur with tubulointerstitial changes in a significantly greater fraction of children over the age of 1 year (P=0.026). Increased glomerular density was associated with severe hydronephrosis (P