Diagnostic of cryptorchidism in horses.

Cryptorchidism in horses is the most common congenital malformation, caused by a failure in the descent of testicles from the abdominal cavity into the scrotum. As a result, there is a partial or complete loss of reproductive potential although the production and secretion of steroid sex hormones and anti-Mueller hormone, as well as behavioral characteristics of the stallion, are maintained. The exact location of the undescended testis is established through a thorough clinical examination of the interior (of the cryptorchid horse), supported by an ultrasound examination of the inguinal region, and the transrectal ultrasound visualization of the bladder area and the inner ring of the inguinal canal. The results of several genetic studies suggest a genetic basis for cryptorchidism. In particularly difficult cases of suspected cryptorchidism in horses (hemi-castrated animals without a known clinical history), it is necessary to determine androgenic hormone levels and the anti-Mueller hormone level and to perform a testosterone production stimulation test with hCG induction (Cox test). The exact location of the retained testicle needs to be known before surgical removal so that optimal decisions can be made regarding the technique of the procedure and selection of appropriate anaesthesia.