Not seeing or feeling a testicle where you would expect it to be in the scrotum is the main sign of an undescended testicle. Testicles form in the abdomen during fetal development. During the last couple of months of normal fetal development, the testicles gradually descend from the abdomen through a tube-like passageway in the groin (inguinal canal) into the scrotum. With an undescended testicle, that process stops or is delayed.