With the spread of prenatal diagnosis, more and more urological disorders are being detected in the fetal stage, but the need for treatment and the prognosis have become a big problem for parents-to-be. Hydrocele is one of the most common fetal disorders. In the fetal period, hydrocele is not recommended for any treatment. At most, ultrasound and MR examinations are recommended during the fetal period, and MRU/CTU and other examinations will be done after birth. As for the judgment of the degree of hydronephrosis, generally speaking, it is based on three aspects of data: the degree of dilatation of the renal pelvis, whether the renal calyces are dilated, and whether the renal parenchyma is thinned by pressure. At present, the majority of hospital tests are only preliminary, only checking the degree of pelvic dilatation, but this is only a very preliminary data, which plays an early warning role. Clinically, the key to determining whether treatment is needed is whether the renal calyces are dilated and whether the renal parenchyma is compressed and thinned. If these two conditions exist, or if severe cases often present with recurrent clinical symptoms such as fever and urinary tract infections, then generally speaking it is time for a surgeon to intervene. Therefore, just looking at the data of the dilated renal pelvis is not enough to determine how far the condition has gone, and it is necessary to improve the relevant data before making a comprehensive judgment! Do not be happy with a data, and do not be sad with a data! As for surgery, the best recovery in hydronephrosis surgery is the surgery for pelvic ureteral junction obstruction, with the best results within 6 months, slightly worse between 6-12 months, and the worst above 12 months.