In an attempt to predict histologic fetal renal dysplasia among fetuses with obstructive uropathy, three antenatal sonographic features (presence of renal cortical cysts, echogenicity of renal parenchyma, and degree of hydronephrosis) were studied. Identification of renal cortical cysts in the kidneys of fetuses with obstructive uropathy enabled accurate prediction of renal dysplasia. Of 49 fetal kidneys with obstructive uropathy, all 15 kidneys with sonographically visible cortical cysts had severe but not necessarily lethal dysplasia (accuracy of positive prediction = 100%). Of 15 obstructed but nondysplastic fetal kidneys, none had sonographically visible cysts (specificity = 100%). The absence of fetal renal cysts on antenatal sonography, however, did not exclude the presence of dysplasia. Assessment of the echogenicity of renal parenchyma and the degree of hydronephrosis are of only limited value in predicting whether an obstructed fetal kidney will show histologic dysplasia.
