Possible causes of large testicles in infants: 1. Infants are born with congenitally underdeveloped testicles, which are usually small in size and equal in size bilaterally, with moderate texture and without pain. If it is indeed confirmed that the size of the testicle is increased, the possibility of congenital testicular tumor should be considered. Ultrasound is recommended to determine whether the testicular parenchyma is enlarged or not, and if necessary, a genetic series is needed to determine whether there is a possibility of congenital testicular tumor. If congenital testicular tumor is confirmed, surgical resection can be considered.2. Congenital syringomyelia, manifested as enlarged scrotum, which is mistaken as enlarged testicle, is more common and may be related to the unclosed syringomyelia after birth. In this case, the size of the testicle is normal, or the volume of the testicle can not be touched due to the accumulation of more fluid. Ultrasound or consultation with a urologist is still recommended to confirm whether the testicles are enlarged or whether there is fluid in the scrotum that causes scrotal enlargement and is mistaken for testicular enlargement. In case of syringomyelia, the syringomyelia may close on its own within 6 months after birth; if it fails to close on its own after 6 months, surgery is recommended after 1 year of age.