Undescended Testicles in Horses

PetMD Editorial
Written by:
PetMD Editorial
Published: November 10, 2011

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)
  • Infertility
  • Stallion-like behavior

Unilateral cryptorchids

  • 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.


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 facility.

Living and Management

The gelding is going to need rest and isolation post-surgery. Surgery, however minor, is painful and uncomfortable. Your veterinarian will advise you on precautions and after surgery procedures you will need to care for your horse as it recovers.

You will need to especially watch out for excessive swelling or inflammation at the surgical site, and for any abnormal behavior from your horse that would indicate that there is an infection so that your veterinarian can be called immediately for consultation.


Most horses with this condition are sterile, but this cannot be taken for granted. If your horse is a cryptorchid, both of the testes will need to be removed entirely since the condition is believed to be inheritable.

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