Neonatal imaging evaluation of common prenatally diagnosed genitourinary abnormalities.

With the implementation of prenatal screening with ultrasound (US) and, more recently, fetal magnetic resonance (MR) imaging, patterns of referral have changed. US remains the first-line imaging modality for evaluating the genitourinary system during the neonatal period and may be enhanced with the use of focused, high-resolution linear images of the pyramids. US has been successful because of its dynamic nature, the excellent morphologic visualization provided in neonates, lack of ionizing radiation, low cost, and lack of need for sedation to acquire the images. US is frequently coupled with mercaptoacetyltriglycine (MAG-3) scanning, providing a powerful combination for morphologic and functional assessment. MR imaging, specifically functional MR urography, has been increasingly used because of its excellent delineation of anatomy achieved without ionizing radiation. MR urography is regarded as a "one-stop-shop examination," as it can provide both anatomical and functional information. It also plays an important role in the evaluation of ureteral ectopia and genital anomalies. Review of available antenatal studies provides invaluable information that may have prognostic significance or may obviate the need for additional examinations or both. Fluoroscopy is typically reserved for assessing vesicoureteral reflux or for detecting urethral abnormalities. In this review, an update on the imaging strategies for common genitourinary anomalies in neonates is presented and illustrated.