"Cystic dysplasia is characterised by the presence of at least one renal cyst (round, anechoic, thin-walled structure) within an abnormal kidney (e.g. hyperechoic parenchyma, absent or reversed corticomedullary differentiation, small kidney size) 1. The abnormality usually involves the entire kidney but can be localised to one segment of a kidney or one moiety of a duplex kidney."