Sonographic findings of fetuses with an empty renal fossa and normal amniotic fluid volume

To review the antenatal sonographic findings and postnatal follow-up of fetuses with empty renal fossa (ERF) and normal amniotic fluid volume.

Sonographic examinations of 13,705 fetuses were retrospectively analyzed and all fetuses with at least one ERF and normal antenatal amniotic fluid volume were included in this study.

Forty cases with antenatal ERF were diagnosed. Prenatal diagnosis consisted of pelvic kidney (n = 24), unilateral renal agenesis (n = 13), horseshoe kidney (n = 2) and crossed fused renal ectopia (n = 1). The prevalence of ERF in the low-risk population approximated 3.2 per thousand. There was no serious renal complication during a mean follow-up period of 30 months except one case of crossed fused renal ectopia requiring hemodialysis.

The underlying cause of ERF in the majority of cases with normal amniotic fluid volume is renal ectopia. Prenatal ultrasonography seems to be highly reliable in diagnosing these anomalies. Prognosis is favorable in the absence of additional extraurinary malformations.