Fetal Magnetic Resonance Imaging in Association With Antenatal Ultrasound in the Diagnosis of Caudal Dysgenesis: Report of Two Cases.

Caudal regression syndrome is a relatively rare congenital disorder that consists of a constellation of caudal developmental growth abnormalities and associated soft tissue anomalies. The severity of its spectrum ranges from lumbosacral agenesis to isolated absent coccyx. We report two cases of caudal regression syndrome that were diagnosed in utero at different gestational ages by prenatal ultrasound followed by fetal MRI for a complete assessment of the associated imaging features. When used in association with antenatal ultrasonography, fetal MRI is particularly instructive in the prenatal diagnosis of caudal regression syndrome since it overcomes the limits of obstetric ultrasound, provides additional information, including associated local soft tissue abnormalities and manifestations of syndromic processes, and allows for a more accurate evaluation of the spinal cord.