The Kidney in Congenital Ureteropelvic Junction Obstruction: A Spectrum From Normal to Nephrectomy

Purpose: Our recent studies of renal histology in congenital ureteropelvic obstruction cases prompted us to review the literature in this regard, focusing on issues of development, normal variation, clinicopathological correlations and pathogenesis. Materials and Methods: The period from 1971 to 2006 was analyzed, including all relevant articles, which were critically reviewed. Results: There have been many studies encompassing the entity of ureteropelvic junction obstruction that include clinical findings, radiographic imaging, pathological examination of ureteropelvic junction obstruction per se and renal biopsies during pyeloplasty procedures. We synthesized this information in a cohesive review with a proposed classification. Conclusions: Congenital ureteropelvic junction obstruction is a spectrum that ranges from the radiological demonstration of apparent physiological ureteropelvic junction obstruction to a disordered ureteropelvic junction, characterized by smooth muscle hypertrophy and fibrosis associated with renal parenchymal changes that may necessitate pyeloplasty or nephrectomy. However, renal biopsies in patients in whom pyeloplasty is done show in most of them relatively well maintained parenchyma, in which overt changes are mainly glomerular. More subtle alterations have been described that relate to shifts in proximal-to-distal tubular ratios. Extreme thinning of the renal parenchyma can occur with only limited tubulointerstitial injury. Recently ureteropelvic junction obstruction was described in a series of genetically altered animals and placed in a more global context, ie CAKUT (congenital abnormalities of the kidney and urinary tract).