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.
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.
If one or both of the testicles remain in the abdomen, the horse is said to be a rig, or ridgling. A stallion that is a cryptorchid should not be used for breeding, as it is suspected to be a genetic problem. The left testicle is more commonly retained than the right.
Symptoms and Types
Bilateral cryptorchids/Complete rig
- Both testicles remain in the abdomen
- Physically appears as a gelding (testes cannot be palpated)
- Stallion-like behavior
- One testicle remains in abdomen
- Will still be fertile from the one descended testicle
Cryptorchidism can be due to hereditary or developmental issues, whereby the testicles fail to drop into the scrotum after birth.
Your veterinarian will begin by palpating the scrotum. If one testicle is missing, this is easily palpated. Occasionally, the horse will need to be sedated for this procedure to be done safely. Once it has been determined that a testicle is not in the scrotum, the next step is to try to locate where it is. Rectal examination may help locate it if it has been retained high in the abdomen. For a better view of the abdomen and inguinal canal, the veterinarian may use ultrasound imaging.
In some cases, if the testes can be located in an easy to access place in the abdomen, a laparoscope can also be used to remove the testes. If the testicle is found in the inguinal canal, the surgery may be more complicated, but can still be performed relatively quickly and easily, with a short recovery time.
If your horse is already a gelding, but is exhibiting stallion-like behavior, your doctor will examine the young horse for higher than normal testosterone levels, along with the abdominal and rectal examinations.