ABSTRACT
Renal pelvis dilatation (hydronephrosis or pyelectasia) is present in approximately 2-3% of all fetuses in mid-gestation. Hydronephrosis is considered to be mild if the antero-posterior dimension of the renal pelvis is 4-7 mm in the absence of calyceal dilatation. Hydronephrosis is classified as moderate/severe if the renal pelvis antero-posterior measurement is over 7 mm or if there is calyceal dilatation.
