To summarize the ultrasonographic findings of fetal mesoblastic nephroma and compare them with pathological findings.

The ultrasonographic images, magnetic resonance images, pathological types, and follow-up results of four cases of fetal mesoblastic nephroma discovered by prenatal ultrasound at Maternal and Child Health Hospital of Hubei Province from January 2003 to December 2018 were analyzed retrospectively.

All the four cases of mesoblastic nephroma were detected in late pregnancy. The diameter of all the masses was larger than 6 cm. All masses were single, unilateral, and solid or cystic solid. The boundary between the mass and surrounding tissue was clear. A little residual kidney echo could be seen in three cases. Abundant dendritic blood flow signals could be detected inside the masses by color Doppler ultrasonography, and all of them were complicated with amniotic fluid. The prenatal fetal MRI imaging features showed different necrotic ranges inside the mass, the boundary of the mass was clear, and the pressed residual renal tissue was visible around it. Three pregnant women terminated pregnancy, and one case underwent ipsilateral nephrectomy after birth, with a good prognosis. In one case showing a complete solid mass, the pathological tissue type was classical, while a cystic-solid mass or mass with predominant solid components was found in three cases, in which the tissue type was cellular or mixed type.

Mesoblastic nephroma is a common fetal renal tumor with characteristic ultrasonographic features, and there is a certain correlation between imaging features and pathological types. The combined diagnosis of ultrasound and magnetic resonance imaging is helpful to diagnose correctly and reduce misdiagnosis.