Imaging of fetal cystic kidney disease: multicystic dysplastic kidney versus renal cystic dysplasia.

With the advent of routine prenatal imaging, the number of renal anomalies identified prenatally has significantly increased; however, the underlying etiologies of these anomalies and the clinical significance of these findings remains unclear. This confusion is especially true for the prenatal diagnosis of cystic renal changes. The terms "cystic kidney disease" and "renal cystic dysplasia" encompass myriad renal diseases. Although renal cystic dysplasia in infants shares many similarities with multicystic dysplastic kidney (MCDK), it is important to distinguish MCDK from other etiologies that would lead to renal cysts, to ensure proper patient diagnosis and appropriate counseling regarding risks and to guide clinical management. The purpose of this review is to highlight the multiple etiologies of cystic kidney disease, including genetic associations, associations with underlying syndromes, and associations with underlying anatomical abnormalities. Here we focus on prenatal imaging, associated pathological findings, and clinical significance, with an emphasis on the defining characteristics of MCDK as compared to other forms of cystic renal disease.