Cryptorchidism in horses

Cryptorchidism is the failure of one or both testes to descend into a normal scrotal position from the abdominal cavity after birth.

Horses with one descended testicle are usually fertile, while horses with both undescended testicle are generally sterile. The testes may be retained anywhere from the abdomen to the inguinal canal, the normal passage route into the scrotum.

Three different forms of cryptorchidism are observed in horses: under the skin in the inguinal area, in the inguinal canal and in the abdomen. In bilateral cryptorchids, most of the time both testes are abdominal.
Cryptorchidism may not be apparent at birth, as the testes do not drop from the abdominal space, through the inguinal canal and ring and into the scrotum – where they remain – until after birth. The time it takes before both testes have descended varies from horse to horse but both testes should be in the scrotum by two years of age. In all cases of one undescended testicle, the stallion will still be able to produce normal amounts of testosterone. Usually, the undescended testicle is much smaller than the descended one.

Symptoms and Types

Bilateral cryptorchids/Complete rig

Both testicles remain in the abdomen
Physically appears as a gelding (testes cannot be palpated)
Infertility
Stallion-like behavior

Unilateral cryptorchids

One testicle remains in abdomen
Will still be fertile from the one descended testicle


Causes

Cryptorchidism can be due to hereditary or developmental issues, whereby the testicles fail to drop into the scrotum after birth.

 Treatment

There is only one method of treatment for cryptorchidism in horses — surgical removal of both testes. This is to prevent the trait from being passed on to offspring. In cases where the undescended testicle is low in the abdomen, the castration can be performed on the farm and is generally uncomplicated. If both testicles have been retained and are high in the abdomen, your horse may require more complicated surgery and will be referred to an equine surgical facilit