Multicystic dysplastic kidney in utero: changing appearance on US.

Serial ultrasound (US) examinations of six cases of fetal multicystic dysplastic kidney were reviewed. In all cases the diagnosis was confirmed by pathologic or neonatal radiologic examination. The in utero appearance on US scans of multicystic dysplastic kidneys sometimes changed dramatically. Furthermore, all of the multicystic dysplastic kidneys changed in size: four enlarged, one shrank, and one initially enlarged and later shrank. Radiologic and laboratory data suggest that multicystic dysplastic kidneys may have the capacity for glomerular filtration. The change in size and appearance of fetal multicystic dysplastic kidneys may result from this residual renal function.