The egg-shell sign: a possible indicator of raised intrarenal pressure.

Prenatal diagnosis of pelvicalyceal dilatation has produced clinical material that we are continually reinterpreting with the help of improving ultrasound equipment. However, the ability to predict the outcome for any one patient with marked dilatation remains poor. We describe a new sign that may help identify those fetuses who have high intrarenal pressure and therefore justify more aggressive management, while obviating the need for intervention for those in whom it is not present. The egg-shell sign consists of a thin crescent of increased echogenicity over a distended calyx and, in this case, was documented to be associated with other features of raised intrarenal pressure.