Synopsis

Antenatal urinary tract dilation (UTD) occurs in 1-2% of fetuses and may be caused by multiple genitourinary anomalies, although mild forms are often transient. UTD can be detected as early as the first trimester as megacystis. Differential diagnosis for fetal UTD can be refined via assessment of the kidneys, ureters, bladder, sex, and amniotic fluid volume. Early detection allows for potential interventions aimed at increasing amniotic fluid volume to allow for critical pulmonary development. While UTD is often detected by ultrasound, fetal MRI has a role in further characterizing renal function and delineating the anatomy of complex urinary tract anomalies.