Urinary tract dilation (UTD-A1) in a fetus with trisomy 21

Transverse and longitudinal view of the fetal kidney(s) demonstrating unilateral urinary tract dilation at 20 weeks in a fetus with trisomy 21. In the transverse view, caliper 2 shows a measurement of 4.1 mm. Note that the measurement is made in the widest part of the intrarenal pelvis with the spine at 12 o'clock to optimize image resolution.