Purebred dogs are at greatest risk. Small, especially toy, breed dogs such as the Pomeranian, Yorkshire Terrier , Dachshund, Chihuahua, Schnauzer, Maltese, and Toy Poodle appear to be at  greater risk but larger dogs, such as English Bulldog and Boxer, also can be affected.

Cryptorchidism is the failure of one or both testicles to drop into the scrotal sac in male dogs. The testicle can be retained in the abdomen or anywhere along the path to the scrotum pouch. Where the testicle is lodged depends entirely on its size at the time of descent.

Both testicles should drop in normal dogs by eight weeks of age. If one or more have not by that time, your dog should be considered as having cryptorchidism. Some texts are more generous and will give a dog until 16 weeks before confirming a diagnosis. Pain is rarely associated with cryptorchidism. One complication that may happen, and will cause severe abdominal pain, is the spermatic cord twisting onto itself. On occasion, other abnormalities are associated with cryptorchidism. They are:

Sometimes testicles that are retained in the abdomen lead to a type of cancer that causes a dog to secrete large amounts of estrogen. This leads to a condition known as male feminizing syndrome.  In this case, a male dog may stop lifting his leg and start to squat like a female. His coat will change. This is often the first symptom owners see. If the dog is unilaterally cryptorchid the normal testicle will often shrink (atrophy). Left unchecked, this condition can lead to pain during urination, infertility, and secondary infections. Excessive estrogen production can also lead to a life-threatening condition called estrogen toxicity.

Cryptorchidism can happen in one or both testicles. If both testicles are retained in the abdomen the dog will likely be infertile. The retained testicles will continue to produce testosterone but not sperm.

Cryptorchidism is an autosomal recessive inherited trait, which means it must be present in both parent’s genetic lines to develop. It is difficult to determine if the dam carries the gene. It is generally determined by her offspring. Breeders are often hesitant to remove an otherwise healthy, sound dog from a breeding program for a seemingly superficial reason. Unilateral or bilateral cryptorchid dogs do not fit the breeding standard and are not accepted in the show ring.

If your dog’s testes do not drop by eight weeks of age he is considered at risk for cryptorchidism. It is possible to wait until your dog is four months before definitely determining a diagnosis. Testicles have been known to drop even later in dogs. On occasion in older dogs, one testicle has been removed for medical reasons (cancer, injury) while the other was spared, usually at the request of the owner.

If this dog later ends up in rescue it can appear unilaterally cryptorchid. The veterinarian will have to look for scars and try to obtain history on the dog for diagnosis. Sparing one gonad is not usually recommended. Adult dogs that are bilaterally cryptorchid will appear much like an unaltered male (save the testicles) due to the fact that the testicles still produce testosterone in the body. These dogs will have the full head and shoulders of an unaltered male. Dogs altered after puberty will have flattened scrotal sacks while the bilateral cryptorchid dog will not.

No treatment other than neutering is recommended. Dogs with cryptorchidism are thirteen times more likely to develop testicular cancer than normal dogs. Fertility may or may not be affected but dogs with cryptorchidism are not recommended to be bred. If an attempt at preserving lineage it often results in complications and pain for the dog and a tarnishing of a name for the breeder.

Recovery is excellent in dogs that are neutered before complications arise. If the retained testicle is left, it may develop cancer, and chemotherapy is sometimes needed.