To investigate the early onset and screening implications of congenital hydronephrosis (CH) in neonates.

From August 1, 2019 to July 31, 2020, a total of 4 811 newborns, 2 566 boys and 2 245 girls, were born in Boai Hospital of Zhongshan. Urological ultrasound screening was performed within 7 d after birth, and children with CH who met the diagnostic criteria were followed up and observed for disease changes and complications in 6 months after birth. The procedures followed in the study were approved by the Ethics Committee of Boai Hospital of Zhongshan (approval No.KY-2019-002-17), and guardians of the subjects all signed the informed consent forms for urinary ultrasound screening.

①From August 1, 2019 to July 31, 2020, 4 811 cases were born in the Department of Obstetrics and had ultrasonographic information recorded, and 268 cases (5.6%) were screened for congenital anomalies of renal urogenital development (CAKUT), of which 248 cases (92.5%) were CH. ②Among 248 neonates with CH, 164 were boys and 84 were girls. And 213, 19, and 16 were mild, moderate, and severe cases, respectively. A total of 111 of 4 811 newborns (2.3%, 111/4 811) had CH suggested by prenatal examination, which was significantly lower than those of screening within 7 d after birth (5.2%, 248/4 811), and the difference between them was statistically significant (χ²=99.408, P<0.001). ③ After 3 months of follow-up, 125 cases (50.4%) hydronephrosis returned to normal, 37 cases (14.9%) improved, 61 cases (24.6%) remained unchanged, 18 cases (7.3%) got worse, and 7 cases had febrile urinary tract infection (UTI). ④After 6 months of follow-up, among 213 mild hydronephrosis children, 164 cases returned to normal, and 4 cases of renal pelvis separation became worse. Of 19 children with moderate hydronephrosis, 11 returned to normal or improved. None of the 16 cases of severe hydronephrosis returned to normal and 12 cases improved. Febrile UTI occurred in 15 cases. 16 cases of severe hydronephrosis and 4 cases of aggravated were examined by magnetic resonance urography (MRU) or computed tomography urography (CTU), and found that ureteropelvic junction obstruction (UPJO) and posterior urethral valves (PUV) were 15 cases and 1 case, respectively. None of them developed from unilateral to bilateral. ⑤ Febrile UTI occurred in 19 children (7.7%, 19/248), including 14 boys and 5 girls. The incidence of febrile UTI in children with severe hydronephrosis (31.2%, 5/16) was higher than that in children with mild hydronephrosis (6.6%, 14/213), and the difference was statistically significant (χ²=411.776, P<0.001). Of the 19 children, 13 were examined by MCU, and 7 were diagnosed with VUR, all of which were mild hydronephrosis. ⑥ Twelve children with severe hydronephrosis improved after surgery, and five children with VUR needed preventive long-term oral administration of low-dose antibiotics. estimated glomerular filtration rate (eGFR) examination in children with severe hydronephrosis, aggravated renal pelvis separation and complications all indicated normal.

Ultrasound screening of CH in early postnatal period is of great significance. Most neonates with mild and moderate hydronephrosis return to normal within 6 months after birth, and most of them with severe and moderate hydronephrosis are pathological obstruction.