To assess the clinical value of genitourinary system ultrasonography in the diagnosis of congenital anomalies of the kidney and urinary tract (CAKUT), and to analyze the clinical significance of fetal genitourinary system ultrasound in guiding prenatal genetic diagnosis.

One hundred and twenty-five fetuses with CAKUT were reviewed and followed periodically by genitourinary system ultrasonography at the Prenatal Diagnostic Center of Huai’an First Hospital Affiliated to Nanjing Medical University from January 2016 to December 2020. They were divided into an isolated CAKUT group and a non-isolated CAKUT group according to whether other structural anomalies were combined. And their genetic results and pregnancy outcomes were analyzed. The χ² test was used to compare the difference of pregnancy outcome and genetic outcome between the isolated CAKUT group and the non-isolated CAKUT group.

Ultrasonoimagedata follow-up of the fetal genitourinary system showed that 17 cases of pyelectasis were found to be self-healing in late pregnancy or 6 months after delivery. There were 41 cases with persistent abnormality but without clinical symptoms, and all of them had good growth and development. There were two cases of misdiagnosis and one case of missed diagnosis. Four cases died of aggravation within 1 year after birth, and two cases with pyelectasis (including 1 case with missed diagnosis) were followed to 6 months after birth, showing indications for surgery and receiving surgical treatment. Forty-eight families chose to terminate pregnancy after rediagnosis by genitourinary system ultrasound, and 11 cases were lost to follow-up. Prenatal genetic examination was performed in 68 samples, and chromosome microarray analysis (CMA) revealed abnormal genetic results in 11 (11/68, 16.2%) cases, including four cases of chromosome aneuploidy abnormality and eight cases of genome copy number variation (one of which had both chromosome aneuploidy and genome copy number variation). The detection rate of genetic abnormalites in the non-isolated CAKUT group (25.0%, 3/12) was higher than that of the isolated CAKUT group (14.3%, 8/56), but the difference was not significant (χ²=0.837, P=0.360). In addition, 10 fetal samples with no abnormal CMA were tested by whole exon sequencing, and one fetus with macrobladder phenotype was detected to carry a heterozygous AQP2 gene mutation inherited from the mother: c.559C>T (p.Arg187Cys), which was judged to be pathogenic.

Genitourinary system ultrasonography examination of CAKUT, as a supplement to fetal system/structure screening, is obviously conducive to improving the accuracy of CAKUT diagnosis, reducing the rate of misdiagnosis and missed diagnosis and helping guide prenatal diagnosis and long-term prognosis evaluation of the fetus.