The testis develops in the abdomen during fetal life and descends all the way to the scrotum on both sides. Given this long journey, it is not surprising that 3% don't make it at birth. When the testis on one side or the other is non palpable, it is said to be cryptorchid. There is a 5% chance that it did not develop normally or that is atrophied from a loss of blood supply in utero (i.e. Torsion).
