During male mammalian development, the testes normally descend from their original position in the abdomen to their final home, the scrotum. When this does not happen, this is known as cryptorchidism or undescended testicle(s).
This failure of the testes to descend is a frequent human birth defect that is associated with infertility and an increased risk of testicular cancer. Both hormonal and genetic factors affect the migration of the testes.
Individuals with cryptorchidism or undescended testis are at an increased risk for developing testicular cancer, with approximately 10 percent of testicular cancer patients reporting a history of this condition. Risks of testicular cancer associated with undescended testes have ranged from 2.5 to 17.1 (presumably per 100,000) (Brown et al., 1987), with the excess risk in cryptorchid men decreasing with increasingly early age at correction (Pottern et al., 1985; Strader et al., 1988a).
Orchidopexy is an operation to move undescended testicles from the abdomen to the scrotum.