Literally, cryptorchidism means "hidden testicle". Abnormal location of the testicle occurs when one or both of the testicles fail to descend completely from the fetal position behind each kidney through their respective inguinal canals into the scrotum. An abdominal cryptorchid has testicle(s) within the abdominal cavity. A horse with testicle(s) in the inguinal canal is called an inguinal cryptorchid or "high flanker". Since cryptorchidism is heritable, cryptorchid horses are considered genetically unsound. For this reason, registration of cryptorchid horses is disallowed by many breed associations.
Cryptorchid castration requires general anesthesia and is therefore more involved than routine castration. The procedure, however, is relatively simple. By using the inguinal extension of the gubernaculum, the testicle can be retrieved without having to dilate the inguinal canal and increase the potential for herniation of bowel into the scrotum. Aftercare consists of one week of stall rest prior to resuming exercise.