Cryptorchidism is the physical absence of one or both testicles in the scrotum of a dog by 6 months of age. The testicles may be retained in the abdomen, or they may be completely undeveloped and absent. If one testicle is retained and one has descended normally, the condition is also called monorchidism.
Causes of Canine Cryptorchidism
The testes are in the abdomen during fetal development. They normally descend through the inguinal canal into the scrotum by the time a male puppy is 6 to 8 weeks old, although this can take longer. Certainly by 6 months of age, both of a puppy's testicles should be fully dropped. Sometimes, one or both testicles are retained in the abdomen and do not descend properly as a puppy matures. Most breeders check male puppies for this condition before placing them in their forever homes. Retained testicles can occur in any male dog of any breed. There is a strong genetic component to this condition; it is thought to be inherited as an autosomal recessive trait. Other causes of cryptorchidism remain a mystery.
Prevention of Cryptorchidism in Dogs
Most authorities agree that dogs with one or both testicles undescended should be neutered early in life and never bred, because of the hereditary component of this condition. Any dogs sired by affected animals probably should be removed from the breeding population as well. Both testicles should be removed to prevent propagation of the condition and reduce the chances of future infection, torsion and cancer in affected animals.
Testicles can descend but later temporarily retract back into the inquinal canal, especially when a young dog is excited, very active or cold. This is not cryptorchidism. If you acquire a male puppy, be sure to ask the breeder whether both testicles have descended. And, when having your dog neutered, ask your veterinarian whether both testicles were successfully removed.
Normal male puppies are born with both testicles in the abdominal cavity. The testes normally descend through the inguinal canal and into the scrotum by the time a puppy is 8 weeks old, although it can occur later. Sometimes, one or both testicles do not descend properly. Cryptorchisism is the failure of one or both testicles to descend completely into the scrotum.
Symptoms of Cryptorchidism in Dogs
Cryptorchidism is often asymptomatic and is rarely painful. In fact, many owners are 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))
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 normally are 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.
Dogs at Increased Risk
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.
Cryptorchidism, which is a condition where one or both testicles do not descend completely into the dog's scrotum by 6 months of age, is not difficult to diagnose.
How Cryptorchidism is Diagnosed in Dogs
Owners of cryptorchid dogs are often unaware of their dog's retained testicles until they take their puppy to a veterinarian for a wellness examination and puppy vaccination series. Most veterinarians normally check male puppies to see if both testicles are in their proper anatomical location. This is detectable by manual palpation. Usually, both testicles are completely descended into the scrotum by 8 to 10 weeks of age. However, in some dogs the process takes longer. If one or both testicles are retained by the time the puppy reaches 6 months of age, he is considered to be a cryptorchid and in most cases should be neutered.
Several laboratory tests are available to help a veterinarian determine whether a supposedly neutered male dog has in fact been fully castrated, or whether he has a retained testicle or testicles. An appropriate dosage of a substance called human chorionic gonadotropin (hCG) can be injected intravenously or intramuscularly, with blood samples being taken several hours before and after hGC administration. Another substance, called gonadotropin-releasing hormone (GnRH), can also be used, in lieu of hCG. Both of these normally stimulate the release of testosterone into circulation in intact male dogs, including those dogs with retained functional testicles. However, if a dog has been properly neutered, his blood testosterone levels will be low and will remain unchanged before and after administration of hCG or GnRH.
Another very useful diagnostic tool is transabdominal ultrasound, which can identify the precise location of undescended testicles, whether they are retained in the abdomen or in the inguinal canal. Abdominal ultrasound is completely painless and non-invasive. Normally, it requires no sedation and is well-tolerated by the patient.
Males with retained testicles should not be used for breeding and cannot be shown in the American Kennel Club conformation ring. If you are buying a male puppy as a potential show dog, it is quite important to be sure that both of his testicles have properly descended by the time you acquire him, to avoid future disappointment and economic loss.
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.
Treatment Options for Cryptorchidism
The therapeutic goals for cryptorchid dogs are all best accomplished by castration and removal of both testicles, whether they are retained or in the proper anatomical location. There is anecdotal evidence that certain medical "therapies," such as hormone injections, may stimulate descent of retained testicles in puppies treated before 4 months of age, although this has not been proven. The ethics of such techniques are highly questionable given the genetic component of this disorder. 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. A procedure that surgically relocates a retained testis into the scrotum – called orchiopexy – is not considered to be ethical among veterinary professionals or reputable breeders. Moreover, artificially relocated testicles carry the same increased risk of becoming cancerous as do testicles that remain retained.
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.