Retained Testicle (Cryptorchidism) in Dogs

What is cryptorchidism?

Cryptorchidism refers to the failure of one or both testicles (testes) to descend into the scrotum. The testes develop near the kidneys, in the abdomen, and normally descend into the scrotum by two months of age. In certain dogs, it may occur later, but rarely after six months of age. Cryptorchidism may be presumed if the testicles cannot be felt in the scrotum after two to four months of age.

If the testicles aren't in the scrotum, where are they?

In most cases of cryptorchidism, the testicle is retained in the abdomen or in the inguinal canal (the passage through the abdominal wall into the genital region through which a testicle normally descends). Sometimes, the testicle will be located in the subcutaneous tissues (just under the skin) in the groin region, between the inguinal canal and the scrotum.

How is cryptorchidism diagnosed?

In cases of abdominal cryptorchidism, the testicle cannot be felt from the outside. An abdominal ultrasound or radiographs (X-rays) may be performed to determine the exact location of the retained testicle, but this is not often done before surgery, as it is not required to proceed with surgery.

Typically, only one testicle is retained; this condition is called unilateral cryptorchidism. A dog that does not appear to have testicles, but is exhibiting male behaviors, can have hormonal tests done to see if he is already neutered (e.g., hCG stimulation test or GnRH stimulation test).

What causes cryptorchidism and how common is it?

Cryptorchidism affects approximately 1%-15% of all dogs. The condition appears to be inherited, since it is commonly seen in families of dogs, although the exact cause is not fully understood. Cryptorchidism occurs in all breeds, but toy breeds may be at higher risk, including toy poodles, pomeranians, and Yorkshire terriers. Approximately 75% of cases of cryptorchidism involve only one retained testicle, while the remaining 25% involve failure of both testicles to descend into the scrotum. The right testicle is more than twice as likely to be retained as the left testicle. 

What are the signs of cryptorchidism?

This condition is rarely associated with pain or other signs unless a complication develops. In its early stages, a single retained testicle is significantly smaller than the other, normal testicle. If both testicles are retained, the dog may be infertile. The retained testicles continue to produce testosterone but generally fail to produce sperm.

One complication of cryptorchidism is spermatic cord torsion (twisting onto itself). If this occurs, there will be signs consistent with sudden and severe abdominal pain. More frequently, a retained testicle will become cancerous. The clinical signs associated with testicular cancer depend on the specific type of cancer.

What is the treatment for cryptorchidism?

The recommended treatment for cryptorchidism is to remove both testicles (neutering). If only one testicle is retained, the dog will have two incisions: one for extraction of each testicle. If both testicles are in the inguinal canal, there will also be two incisions. If both testicles are in the abdomen, a single abdominal incision will allow access to both.

What if I don't want to neuter my dog?

There are several good reasons for neutering a dog with cryptorchidism. First, neutering removes the genetic defect from the breed line. Cryptorchid dogs should never be bred. Second, dogs with a retained testicle are more likely to develop a testicular tumor (cancer) in the retained testicle. Third, as described, the testicle can twist, causing pain and requiring emergency surgery to correct. Finally, dogs with a retained testicle typically develop the undesirable characteristics associated with intact males, such as urine marking and aggression.

The risk of developing testicular cancer is estimated to be at least ten times greater in dogs with cryptorchidism than in normal dogs.

What is the prognosis for a dog with cryptorchidism?

The prognosis is excellent for dogs that undergo surgery early, before problems develop in the retained testicle. The surgery is relatively routine, and the outcomes are overwhelmingly positive.