The role of color and power Doppler ultrasound in the prenatal diagnosis of sirenomelia.

Sirenomelia is a rare congenital abnormality characterized by a variety of anomalies involving the lower limbs, severe oligohydramnios, bilateral renal agenesis, anorectal atresia and aberrant fetal vasculature. The prenatal diagnosis and differentiation from isolated bilateral renal agenesis is severely limited by the accompanying oligohydramnios that hinders visualization of fetal anatomy. We present three prospectively assessed cases of sirenomelia, two of which had bilateral renal agenesis, and all of which had a single umbilical artery derived from the aberrant vasculature that accompanies the syndrome.