Pathogenesis of dysplastic kidney associated with urinary tract obstruction in utero.

Renal dysplasia is the major cause of chronic renal failure in children, and is commonly associated with urinary tract obstruction. There are two phenotypes of renal dysplasia associated with urinary tract abnormality, multicystic dysplastic kidney (MCDK) and obstructive dysplasia (ORD). Previous observations by Potter and co-workers suggested that cystic dilatation of the ureteric bud ampula was the cause of renal dysplasia. In this context, our recent investigation of human fetal dysplastic kidneys provided an alternative explanation for the evolution of renal dysplasia. We suggested that in utero urinary tract obstruction may cause urine retention in functioning nephrons and lead to glomerular cysts in the nephrogenic zone. The mechanism was common to MCDK and ORD, albeit at different sites of obstruction. Expansion of glomerular cysts with tubular dilatation (cysts) disturbs the subsequent nephron induction and may contribute to the abnormal development of fetal kidneys.