Copyright June, 2000. Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada. Material may not be changed without the permission of the authors.
Cryptorchidism is a developmental defect in both animals and humans.
During the fetal life, the testes move from a position inside the abdominal cavity through a space called the inguinal canal. This process is completed by the time the foal is two weeks of age. In one study of horses, the failure of the left and right testicles to descend into the scrotum occurs with nearly equal frequency. In bilateral cryptorchids, most of the time both testes are abdominal. The retention of testes is a complex, incompletely understood process involving genetic, hormonal and mechanical factors.