Cryptorchidism in Dogs
The testes normally descend into the scrotum while an animal is very young. For dogs, the descent to the final scrotal position is expected to be complete by the time the puppy is two months old. It may occur later in some breeds, but rarely after six months. In beagles, the testis is at the exterior inguinal ring by the fifth day, between the inguinal ring and scrotum by day 15, and in the scrotum by day 40. Cryptorchidism is a condition characterized by incomplete or nonexistent descent of the testes.
When the descent of one, or both, of the testes does not happen, the testis that has not descended is retained somewhere in the lower part of the body. For example, they are sometimes retained in the inguinal canal - a passage in the groin that conveys the spermatic cord to the testes. If the testis is in the inguinal canal, it can be felt (palpated) during a physical examination. If the testis is deeper in the abdomen, it will be difficult to palpate or identify with an x-ray. Ultrasound is the best available option to determine the size and location of the testis if it is in the abdomen. This abnormality can occur in almost all breeds of dogs, but toy and miniature breeds are at a significantly higher risk. In certain populations, shepherds, boxers, and Staffordshire bull terriers also have a greater incidence of this condition. The right testis fails to descend twice as often as the left. Ranges of 1.2 to 3.3 percent of cases have been reported, with a proportional increase in purebred dog populations. It is thought to be genetically passed on as a sex-limited chromosomal recessive trait.
The condition or disease described in this medical article can affect both dogs and cats. If you would like to learn more about how this disease affects cats, please visit this page in the PetMD health library.
Symptoms and Types
This condition is rarely associated with pain or any other sign of disease. However, acute onset of abdominal pain generally indicates that the spermatic cord of the retained testes has become twisted, cutting off the blood supply to the testis. Many times, this testis will develop tumors, which is symptomized by feminine behavior. The risk of testicular cancer is thought to be approximately ten times greater in affected dogs than in normal dogs.
What causes the testis to remain undescended or incompletely descended is unknown. Some of the reasons that have been concluded so far have pointed to a genetic flaw. Conversely, the condition may not have a hereditary predisposing factor at all, but may still be linked to an occurrence that took place in the intrauterine environment during the formation of the developing fetus (i.e., pregnancy). An adverse condition or environmental factor can lead to a congenital malformation, perhaps affecting only one in a litter. This is not a preventable condition.
To arrive at a diagnosis, your veterinarian will use ultrasound as the most reliable diagnostic tool to locate the undescended testis, along with palpation (touch) of the groin and abdomen to locate the testis.
The castration of both testes is generally recommended. Even if one testis has descended and the other has not, your veterinarian will most likely counsel you to have both removed. Surgical placement of an undescended testicle into the scrotum is considered unethical. There has been some anecdotal evidence that human hormones, when given to dogs less than four months old, will motivate the descent of the testis. Descent after four months of age is rare, and after six months, unlikely. Although there may be no outward symptoms or obvious repercussions of the condition, it is not advised to leave the undescended testis in the body, since there is a risk of testicular cancer with retained testes. Further, a dog with this condition should be castrated by the time it has reached four years of age.