Antenatal hydronephrosis: thresholds of renal pelvic diameter to predict insignificant postnatal pelviectasis

We tested the parameters of gestational age and renal pelvic anteroposterior (AP) diameter of antenatally detected pelvicaliectasis for their ability to determine insignificant postnatal renal pelvic dilatation. A retrospective analysis of 10,365 antenatal sonograms revealed 121 kidneys with pelvicaliectasis, from which 99 sonograms with sufficient postnatal follow-up were reviewed. Gestational ages were classified as <20, 20-30, or >30 weeks. Thresholds of renal pelvic AP diameter in each gestational period that were predictive of postnatal insignificance were determined to be <6, <8, and <10 mm, respectively. Insignificance postnatally was defined as no or minimal renal pelvic splitting (Society for Fetal Urology grade