Fetal hydronephrosis is a clinical syndrome with varying degrees of dilatation of the fetal collecting system due to a range of etiologies. With a prevalence of approximately 1.4%, obstetricians, pediatric urologists, and ultrasonographers are often faced with the diagnosis, evaluation, and treatment of fetal pyelonephrosis. However, the diagnosis and treatment of fetal pyelomeningocele is still controversial internationally, with four main areas of controversy: diagnostic criteria, site of obstruction, timing of treatment, and preservation or non-preservation of the affected kidney. There is no unified operation standard for ultrasound screening of fetal hydronephrosis, which seriously affects the reference value of the test results for diagnosis and the lack of comparability of test results among different operators, which affects the follow-up and evaluation of the child’s condition. Many medical personnel still have more confusion in clinical work and are not able to make scientific prenatal diagnosis, evaluation and guide treatment of fetal hydrocele. The purpose of this conference is to address the problems in the diagnosis and treatment of fetal hydronephrosis at this stage and to discuss the treatment process of fetal hydronephrosis. Screening methods for fetal hydronephrosis It is recommended to unify the measurement specifications for ultrasound screening of fetal hydronephrosis. Ultrasound screening of fetal hydronephrosis should be performed every 4 weeks starting at 20 weeks of gestation, with attention to other positive ultrasound indications other than hydronephrosis, such as dilated ureter or abnormal bladder development, etc. Ultrasound screening of fetal hydronephrosis should include the following components: ensure consistency of the child’s underlying conditions at the time of measurement, and record whether it is before or after urination; include sagittal and coronal views of the kidneys during ultrasound examination; and indicate that The thickness of the renal parenchyma should be measured and differentiated between the cortical and medullary divisions, and between the thickness of the affected and healthy renal parenchyma; the bladder volume should be measured before and after urination to compare the pelvic separation before and after urination. These are useful for guiding the assessment of renal development during fetal life, the possibility of developing renal infection after birth, and the need for prophylactic antibiotics. In some fetuses with multisystemic malformations, karyotype analysis and multisystemic malformation examination are recommended. MRI should be performed for suspected cases of renal cystic change, giant ureteropathy, posterior ureteral valve, syndrome of Megan’s belly, duplication malformation, ectopic ureter, ureteral cyst, etc. Fetuses with clinically diagnosed hydronephrosis are reviewed by ultrasound every 4 weeks until birth. Most scholars at home and abroad define the degree of congenital hydronephrosis according to the anterior-posterior pelvic diameter (APD), and the clinical diagnosis of fetal hydronephrosis is made when the separation is >10 mm. After the diagnosis of fetal hydronephrosis, its grading is of guiding significance for treatment. There are three commonly used criteria for the diagnosis and grading of fetal hydronephrosis: Grignon grading, Arger grading, and the 1988 American Academy of Fetal Urology criteria; Grignon grading: Grade I is 15 mm dilatation of the renal pelvis with moderate dilatation of the renal calyces; Grade V is moderate dilatation of the renal calyces and thinning of the renal parenchyma; Arger grading: Grade I is 20 mm dilatation of the renal pelvis as severe hydronephrosis. Treatment of fetal hydronephrosis 1. Treatment during fetal period and at delivery: Fetal surgical treatment emphasizes timely surgical intervention before fetal diseases affect normal fetal development or damage important organ functions, and has positive significance for the treatment of malformations that can threaten fetal life in fetal period. At present, fetal surgery is still in its infancy, and there are many serious surgical complications and ethical issues. At present, fetal surgery has not been carried out in China, fetal prenatal diagnosis and EXIT, neonatal surgery early intervention model is the better model at present, laying the foundation for the future development of fetal surgery. 2.Management at birth: including low amniotic fluid, genital malformations, other malformations on the neonatal period, and the management of the newborn at delivery. For fetuses with excessive kidney volume that affects natural delivery, cesarean delivery is the preferred method of delivery. 3. Improve examination: Most children with prenatal diagnosis of hydronephrosis can be examined on an outpatient basis after birth. A series of tests are performed immediately after birth to rule out associated malformations. It is controversial whether radiological tests are done in newborns. Our opinion favors the need for VCUG after birth in children with prenatally diagnosed hydronephrosis, i.e., if the child has a dilated renal pelvis >10 mm or a dilated ureter. VCUG is necessary even if postnatal pelvic fluid has disappeared on ultrasonography. In children with high suspicion of reflux or incomplete emptying, if VCUG shows no reflux, a second slow injection of contrast into the bladder for VCUG is required. The child needs to be reviewed regularly for ultrasound after birth. Due to the physiological dehydration of the newborn after birth, ultrasound examination needs to be performed after 3 d after birth, otherwise it will affect the ultrasound judgment of hydronephrosis. The first ultrasound examination is often chosen to be performed 3-4w after birth. When the child’s postnatal repeat ultrasound suggests severe pelvic dilatation (collecting system separation >15mm) with ureteral dilatation, excretory urography is necessary to assess urinary tract obstruction and renal function, and the ideal age for examination is one month after birth, and 99Tc nuclear scan can also be selected. 4. Hydrocele caused by vesicoureteral reflux, megaureteral disease, posterior ureteral valve, Meconium abdominal syndrome, ectopic ureter, ureteral cyst, etc. should be treated by early surgery. Children with UPJO with mild hydronephrosis (APD15mm or with ureteral dilatation, calyces dilatation and cortical thinning should be included in surgical treatment. Children with severe hydronephrosis (APD>20mm) or with dilated calyces, dilated renal cortex, and dilated ureters should be treated surgically. All non-surgical children under conservative observation will require surgical treatment to relieve obstruction if a nuclear scan indicates impaired renal emptying. Radionuclide scans suggest divided renal function.