Prenatal diagnosis and outcome of fetal hyperechogenic kidneys in the era of antenatal next-generation sequencing*

Background: Fetal hyperechogenic kidneys (HEK) are associated with a wide range of etiologies and prognoses. Prenatal counselling and management can be extremely challenging, especially for isolated HEK.Methods: A total of 28 pregnancies were screened by ultrasonography with HEK from March 1, 2016 to December 31, 2020. Genetic testings for aneuploidy and copy number variations (CNVs) are routine during the investi-gation for etiologies of fetal HEK in our unit. Trio-whole exome sequencing (WES) was offered to the family when karyotyping and microarray were not diagnostic. A systematic review (SR) was conducted to use the authori-tative literature retrieval databases describing genetic testings' results in prenatal HEK cases.Results: In the 28 HEK fetuses, 2 (7.14%) cases were identified with chromosome abnormalities and 6 (21.43%) cases were detected with pathogenic CNVs. Through trio-WES analysis, pathogenic or likely pathogenic varia-tions were detected in the following genes: PKD1, BBS2, BBS9, HNF1B, PKHD1 and ETFA in another 10 (35.71%) fetuses. And the remaining 10 (35.71%) cases were undiagnosed. The pooled data from all reviewed studies indicate that HNF1B gene heterozygous deletion or mutation are the most common genetic causes associated with HEK.Conclusion: This is the first study to accurately describe the genotype ratio at different levels of genetic testing associated with fetal HEK. Our study has suggested that trio-WES could improve the detection rate and efficiency of identification genetic pathologies in fetuses with isolated HEK. The WES results provide new evidences to guide prenatal counseling and management.