Undescended testicles in dogs

A dog in which one or both testicles have not descended and are missing from the scrotum is said to be cryptorchid. Cryptorchidism is inherited as an autosomal recessive trait. Mature dogs with two undescended testicles are sterile. A cryptorchid dog with one descended testicle may be fertile, but should not be used for breeding.

If one testicle is actually missing and the other is present, the dog is said to be monorchid.

The testicles usually descend into the scrotum by 6 to 8 weeks of age, but may not descend until 6 months of age. Occasionally a testicle can be felt in the scrotum at one time but not at another. The testicles can retract up into the inguinal canal when a puppy is cold, excited, or actively playing. These puppies are not cryptorchid.

Treatment: Hormone injections have been used to stimulate testicular descent in puppies, but the rationale is questionable. In some cases descent would have occurred spontaneously. Furthermore, cryptorchid dogs are not candidates for breeding because the condition is heritable.

Removing both testicles is the treatment of choice because of the risk of developing testicular neoplasms, which may be as high as 50 percent in dogs with undescended testicles. During surgery, it is important to find and remove the cryptorchid testicles. This may involve making an abdominal incision.