Undescended Testicles (Cryptorchidism) in Dogs

Key Takeaways

Undescended testicles (cryptorchidism) is observed when one or both testicles are not present in the scrotum after 4 months of age.

• Cryptorchidism results when the connective tissue from the scrotum to the testicles fails to develop properly

• Due to the higher temperature in the abdomen, sperm are not produced by retained testicles, but testosterone is

• Ultrasound is the most useful diagnostic tool for attempting to locate a missing testicle

• Undescended testicles are hereditary, and are a common defect in dogs

• Retained testicles are more likely than scrotal testicles to experience life-threatening conditions like testicular torsion and testicular cancer

• Neutering eliminates the chances for complications and is more involved compared to the same procedure for a dog with scrotal testicles, as the precise location of the testicle(s) can be difficult to find

A Closer Look: What is Cryptorchidism in Dogs?

Undescended testicles are not an emergency, but if this is detected, neutering is recommended to correct the problem. If undescended testicles are left in place, they increase the chances of testicular cancer or testicular torsion. Cryptorchidism is common in dogs, with rate of incidence estimated to be 0.8-15%.

Possible Causes

Undescended testicles are caused by incorrect development of the connective tissue that attaches the testicles to the scrotum. This leads to one or both of the testicles being retained in the abdomen or the inguinal canal, which is the passage through the abdomen into the genital area or the area between. Undescended testicle(s) are hereditary. Most cases result in one of the testicles descending into the scrotum, while the other remains in the abdomen or inguinal canal. This is known as unilateral cryptorchidism and happens in approximately 75% of cases. If both testicles remain undescended, this is known as bilateral cryptorchidism.

Risk Factors

Undescended testicles result in higher chances of testicular torsion and testicular cancer if they are left in place.

Testing and Diagnosis

Testicles usually descend to the scrotum by the time a puppy is four months old. Diagnosis is self-evident when the testicles are not palpable within the scrotum. Sometimes the missing testicle is palpable in the groove between the inner thigh and the abdomen. If the testicle is not palpable in the scrotum or along the inguinal groove, it is either in the canal, somewhere in the abdomen, or it was never formed. 

Ultrasound is helpful for attempting to find testicles in the inguinal canal or abdomen, but it’s not always possible to locate the testicle without exploratory surgery. The hunt is complicated by the fact that until it is located, it is uncertain if the missing testicle even exists.

If neither testicle is palpable in the scrotum or along the inguinal fold, blood hormone levels are used to determine if testicular tissue is present somewhere in the body. If the levels are low, the conclusion is drawn that the dog has either been neutered or did not develop testicles at all.    

The only treatment for undescended testicles is surgery, as leaving the undescended testicles could result in testicular torsion or higher chances of testicular cancer.

Similar symptoms

Undescended testicles could be mistaken for anorchidism, which is where neither testicle exists. It can also be mistaken for monorchidism which is where one testicle does not exist.

Associated Symptoms

Pain is rarely associated with undescended testicles. In rare cases, the dog could experience spermatic cord torsion which would result in severe abdominal pain. If the retained testicle is left in place and only the obvious testicle is removed at the time of neutering, the dog will be sterile, but will continue to exhibit normal secondary male characteristics as a result of testosterone production by the retained testicle.

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