With the development and availability of ultrasound technology, hydrocele in the fetus is one of the most easily detected congenital urologic developmental anomalies. The most common cause of hydrocele is obstruction of the pelvic-ureteral junction, and the vast majority do not require postnatal surgical intervention. It has been reported in the literature that less than 25% of patients require surgical intervention at 4 years of postnatal follow-up. Unilateral hydronephrosis secondary to obstruction has a 100% postnatal survival rate and a fairly good prognosis. Therefore, when hydrocele is detected prenatally, it is important to consult with an obstetrician and urologist and to establish a postnatal follow-up plan. However, if prenatal ultrasound reveals severe bilateral hydronephrosis with bilateral ureteral dilatation and decreased amniotic fluid, it may indicate that the fetus has posterior urethral valve disease, which has a poor prognosis and is prone to renal failure, and requires prenatal consultation with an obstetrician and urologist and abortion if necessary.