How is fetal hydronephrosis diagnosed?

Maternal ultrasound: Can sometimes already be detected after 10-12 weeks gestation. More commonly in mid to late pregnancy. Sometimes suspected and found in presence of oligohydramnios (reduced amniotic fluid).

Fetal ultrasound.: Prenatal sonography should pick up 90% of fetal hydronephrosis after 18-20 weeks (more so in the last three months of pregnancy).