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An undescended testicle (cryptorchidism) is one that remains inside the body and has not moved down into the scrotum. Normally the testicles, which form inside the abdomen of a male fetus, descend into the sac beneath the penis (scrotum) by the time the baby is born.

One or both testicles may be affected. Often the testicle will descend after birth, usually within the first 3 months. If this does not occur, a doctor may recommend surgery (orchiopexy) to move the testicle into the scrotum.