Fetal obstructive uropathy without renal dysplasia: a study of the renal findings in 13 cases presenting with megacystis.

Objective: Metanephric maldevelopment is a frequent sequela of fetal urinary tract obstruction, particularly when maternal oligohydramnios and massive lower urinary tract dilatation are present. The kidneys in 13 subjects at an estimated 15 to 39 weeks of gestation with distal urinary tract obstruction presenting with severe megacystis not associated with renal dysplasia were examined to discover other manifestations of impaired renal development.

Methods: Complete autopsy specimens in 13 cases of severe megacystis in which 1 and 2 kidneys in 3 and 10, respectively, were free of dysplastic features were examined to determine whether there were abnormalities in the cortex and medulla that indicated impaired renal development.

Results: The kidneys in 9 cases had various abnormalities indicative of perturbed renal development, such as the premature disappearance and phenotypic alteration of nephrogenic zone cells, a decreased number of nephron generations and medullary collecting duct abnormalities. In 4 cases the kidneys had developed normally.

Conclusions: The majority of subjects with urinary obstruction but nondysplastic kidneys had significant renal abnormalities that would have limited future functional capacity. However, abnormal development is not inevitable even in severe fetal obstruction, suggesting that select cases may benefit from fetal intervention.