What are Undescended Testicles?
When one or both of the testicles fail to descend into the scrotal sac, the horse is referred to as a rig, a ridgling, or more commonly, a cryptorchid. The term cryptorchid literally translates to hidden testes (crypt = hidden, orchid = testes). While the equine veterinary community, including veterinarians, specialists, and researchers, cannot state for sure what causes cryptorchidism, it is strongly suggested that it is developmentally-related, and based on heredity. Supporting the position that cryptorchidism is an inherited condition is its tendency to arise more often in particular breeds, such as Quarter Horses, Saddlebreds, Percherons, and ponies. If the condition is a developmental defect, this testicular abnormality may be traceable to a particular phase while in utero. This kind of knowledge will be assistive when looking toward prevention. Currently, due to the relative small number of cryptorchidic horses, long-term studies have not been able to confirm or deny genetics as a cause. Other considerations involve hormonal or mechanical causes, and some researchers believe the cause is a matrix of the three. Moreover, treatments are happening in isolation in different parts of the U.S. and Canada, so the success of surgical versus hormonal treatments cannot be measured as a whole. While many equine veterinarians are in favor of surgical treatment, hormonal preparations are currently being used by a limited number of equine specialist in the U.S.
In a developmentally normal horse, the testicles will be descended at birth. Other colts may take a longer time, though in horses still undescended between 18-24 months, surgery or another form of treatment is likely to be needed. Some cryptorchidic horses have one testicle retained from the scrotal sac, while other horses retain both, a condition called bilateral undescended testes. The difference between unilateral and bilateral retention is significant because the unilateral type is fertile, while the bilateral type is sterile. A stallion with one descended testicle is fertile, but has a low sperm count. This horse should not breed in case of genetic abnormality. While the bilateral type is infertile, he will still demonstrate stallion-like behavior, causing breeding frustrations for female horses. The complications of undescended testicles lead many veterinarians to recommend castration. If the abnormality is indeed genetic, castration could help to prevent further cases of undescended testicles in horses.
Cryptorchidism in horses is a condition when one or both testicles fail to descend into the scrotum from the abdominal cavity.
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Symptoms of Undescended Testicles in Horses
Symptoms of the condition will be observable or, in the case of testes in the scrotal sac, palpable. An equine veterinarian should be consulted in the case of any genital abnormality.
- Lack of visible testicles
Three forms of cryptorchidism have been observed in horses.
- Under the skin in the inguinal area
- Inside the inguinal canal
- In the abdomen
Some horses are bilateral cryptorchids, in which both testicles remain in the abdomen, and others have one descended testicle. These are often referred to as monorchids.
Causes of Undescended Testicles in Horses
Cryptorchidism is likely a congenital, inherited abnormality; however, its cause is not fully determined. Other possibilities for the abnormality may include hormonal or mechanical factors.
Diagnosis of Undescended Testicles in Horses
Visible or palpable abnormality in the testicles will likely direct the diagnosis. The veterinarian will do an external palpation as well as a rectal examination. Ultrasound is often used to back up the physical exam, and helps to determine if and where the testes are being retained. In the absence of observable testis, the administration of hormone therapy may be used for diagnostic purposes. Blood testing, measuring estrogen and testosterone, is also used to help diagnose a cryptorchid.
Treatment of Undescended Testicles in Horses
In horses retaining both testicles in a high position, surgery in a facility is the preferred option. Current surgical methods may include the use of a laparoscope to remove both testes, which allows for a less invasive and painful procedure. If the undescended testicle is in the lower abdomen, castration can be performed normally. Of course, this is preferable. Currently, hormonal preparations in the form of injections are being explored, but outcomes are not yet documented.
Recovery of Undescended Testicles in Horses
The horse’s recovery will depend on the type of procedure used. Post-surgically, any horse will need extra rest in isolation. The veterinarian will likely prescribe medication in the case of pain and swelling. It is important to watch for both physical and behavioral changes in the horse, especially signs of infection or aggression.