Prenatal imaging of upper urinary tract abnormalities: when is MRI useful?

Upper urinary tract abnormalities are commonly encountered on fetal imaging. While ultrasound (US) remains the primary imaging modality for evaluation of the fetal kidneys, magnetic resonance imaging (MRI) can play a significant complementary role in the diagnosis and management of these patients with upper urinary tract abnormalities. This paper will review the most common prenatal pathologies encountered in the kidneys, including urinary tract dilatation (UTD), renal agenesis, renal ectopia, multicystic dysplastic kidney (MCDK), and other cystic renal diseases, and will include a discussion of when and why fetal MRI should be considered in these diagnoses. Images from prenatal US and fetal MRI examinations will be included.