Cryptorchidism is the failure of one or both testicles to descend normally from the abdomen into the scrotum of young intact male dogs. The goals of treating this disorder are to prevent subsequent torsion of the retained testicle(s) and to prevent development of testicular cancer. Treatment is also designed to prevent propagation of genetic abnormalities and to eliminate undesirable male behavioral traits associated with testosterone.

Cryptorchidism is often asymptomatic and rarely painful. Many owners are often unaware that their dog has the disorder. However, it is quite important to diagnose and treat this condition, because dogs with retained testicles are at an enormously increased risk of developing testicular cancer. Signs of retained testicles that owners may observe include:

  • Noticeable absence of one or both testicles in the scrotal sac, either visibly or upon palpation (the dog’s scrotum looks empty and loose)
  • Leg-lifting during urination earlier than expected in a supposedly neutered dog
  • Exuberant male breeding behavior (mounting, “humping”) in a supposedly neutered dog
  • Intense interested in intact females, particularly when they are in season, in a supposedly neutered dog
  • Dog-aggression, especially towards intact males, in a supposedly neutered dog
  • Successful mating (cryptorchid dogs may be able to impregnate female dogs, depending upon the location of their retained testicle(s))
  • Testicular infection
  • Testicular tumors
  • Acute onset of extreme abdominal pain (from torsion or twisting of the spermatic cord of the retained testes)
  • Symmetrical hair loss (alopecia) along the trunk and flanks
  • Pendulous preputial sheath
  • Darkened (hyperpigmented) external genitalia
  • Feminization (from estrogen secreted by Sertoli cell tumors in retained testes)

While signs of cryptorchidism are normally mild or nonexistent, the condition does carry some risks. Retained testicles develop disease at a much higher rate than do normal testicles – including infection and testicular cancer. They also are prone to twisting, or becoming “torsed”, which causes acute-onset of extremely severe abdominal pain. Some cryptorchid dogs can impregnate females, which is usually quite surprising to owners who have had their dog “neutered,” but unbeknownst to them only one testicle was removed. Other cryptorchid dogs may try but be unable to reproduce successfully due to impaired sperm development in the retained testicle. Mature dogs with two retained testicles are usually sterile.

Retained testicles can occur in any male dog of any breed. Purebred toy and miniature breeds seem to be at significantly higher risk, especially Yorkshire Terriers, Toy Poodles and Pomeranians. Some family lines of German Shepherds, Staffordshire Bull Terriers and Boxers also are predisposed. There is thought to be a strong genetic component to this condition. It is much more common for affected dogs to only have one retained testicle (unilateral cryptorchidism) rather than two (bilateral cryptorchidism). Interestingly, the right testis in dogs is retained almost twice as frequently as the left. The reason for this statistical anomaly is not known.

The treatment for cryptorchid dogs are castration and removal of both testicles, whether they are retained or in the proper anatomical location. Most breeders agree that cryptorchid dogs should not be considered candidates for breeding. Their fathers, male siblings and any male offspring have an increased chance of being genetic carriers of the condition, even if they do not have it themselves.

Undescended testicles can be difficult to locate. Transabdominal ultrasound can be very helpful to veterinarians trying to find retained testes, especially before surgery. Removal of retained testicles usually is more expensive than a normal castration procedure, because it almost always involves abdominal exploration. In rare cases, a retained testicle can be manually massaged down into the scrotum, making it easier and less costly to remove.

After surgical removal of undescended testes, the dog will need some down time to recover. He should be given soft, thick bedding in a quiet area, with free access to fresh water. His activities should be restricted for a week or two, until the surgical incision has healed and the swelling has resolved.

Dogs with retained testicles have a much greater risk of developing testicular cancer than do dogs whose testicles both descend normally. In fact, neoplastic tumors occur in roughly 50 percent of undescended testicles – a ten-fold increase over the risk of cancer in non-retained testes. Surgical correction of cryptorchidism should involve removal of both testicles, regardless of their location in the scrotum, inguinal canal or abdomen. With this treatment and appropriate post-operative supportive care, the prognosis for affected dogs is excellent.


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