One extra testicle is considered to be caused by congenital abnormal testicular development, enlarged epididymis, testicular tumor and other factors. 1. Congenital testicular developmental abnormality: generally means that it has been formed during the embryonic period, usually related to chromosomal abnormality, which is easy to cause multiple testes, resulting in the illusion of one more testis. 2. Enlarged epididymis: mostly developed from epididymitis, repeated inflammation stimulation, easy to cause epididymis enlargement, usually mistaken for testicles. 3. Testicular tumor: when the tumor in the testicular area gradually increases in size and is similar to the size of the testicle, it may also be mistaken for the testicle, which can be accurately analyzed through pathological biopsy. If abnormal testicular growth is found, it is recommended to seek medical treatment in time, and then diagnose and analyze it through local ultrasound and pathological examination to understand the cause of the disease and then actively cooperate with the treatment.