Delayed opacification in congenital multicystic dysplastic kidney, an important Roentgen sign.

Two cases of delayed opacification of multiple irregular cystic spaces are reported in unilateral congenital multicystic kidney. This finding should be added to the basic excretory urographic sings of poor function, cystic spaces on total body opacification, and calyceal crescents, and indicates the need for delayed films in all such cases. Reevaluation of the necessity for further diagnostic study and nephrectomy are discussed.