Undescended testicle dog problems (+ cats): What to know, what to expect and what to do?

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Cryptorchidism or undescended hidden testes is a common problem in dogs
Cryptorchidism or undescended hidden testes is a common problem in dogs

Undescended testicle dog problems can be serious. Cryptorchidism is the scientific term for undescended testicles in dogs. Cryptorchidism in dogs is a common problem in dogs and cats.
Actually, the word cryptorchidism literally means “hidden testes”, a condition occurring in other mammals, including men (The prefix crypto comes from the Greek word kryptos and the word orchid means testicle). This veterinary term means in plain words undescended testes. An animal with both testes undescended is called cryptorchid and one with just one undescended testis is called monorchid (mono = one). Testes should normally descend to the scrotum (a skin pouch in male animals) around the time of birth in most mammals like dogs and cats.

Faulty testicular descent mechanisms   impair testis migration and one or both testes can become retained   inside or near the abdominal cavity.
Cryptorchidism or undescended hidden testes is a common problem in dogs affecting from 7 to 10% of dog populations. Faulty testicular descent mechanisms impair testis migration and one or both testes can become retained inside or near the abdominal cavity.

How frequent is cryptorchidism in dogs and cats?

Cryptorchidism or undescended hidden testes affects from 7 to 10% of dog populations. This is less of a problem with cats (scientific studies mention that a little more than 1% of cat populations carry the condition).

Faulty testicular descent mechanisms impair normal testis migration (that should complete around birth) and one or both testes can become retained inside or near the abdominal cavity.

In what breeds is cryptorchidism more common?

Undescended testes are more common in some dog breeds (see the list below) and can bring about serious health problems to dogs (more about this in a minute).
Cryptorchidism is more common in German shepherds, boxers, and chihuahuas.
In 1985, a large scientific study presented a larger list of breeds with a high probability of having undescended testes. As you can see from the following list, many of the dogs at risk belong to small or miniature dog group of breeds:

  1. Toy Poodle
  2. Pomeranian
  3. Yorkshire Terrier
  4. Miniature Dachshund
  5. Cairn Terrier
  6. Chihuahua
  7. Maltese
  8. Boxer
  9. Pekingese
  10. English Bulldog
  11. Old English Sheepdog
  12. Miniature Poodle
  13. Miniature Schnauzer
  14. Shetland Sheepdog

Which testis has a higher chance to be cryptorchid?

A monorchid testis (just one retained testis) is loosely called cryptorchidism (the pair of testes is undescended).
Normally, testes descend inside the abdominal cavity (where organs like intestines and kidneys are located) and pass through a small hole in the abdominal wall (inguinal ring) to the inguinal (between the thighs) region before settling in the scrotal pouch.
Among dogs, right-sided inguinal (near the testis) cryptorchidism is more frequent, followed by right-sided abdominal cryptorchidism (the testis is retained in the abdominal cavity).
In cats, inguinal is generally the most common form of cryptorchidism and no side is more frequent.

Cryptorchisdism in dogs means that testes are undescended to the skin pouch called scrotum
Cryptorchisdism in dogs means that testes are undescended to the skin pouch called scrotum. Common misplacements of testes can be abdominal and inguinal.

Why testes must be outside the body in the first place?

Logically, testes, having the epic responsibility of producing offspring (just like the ovary), should be protected inside the abdominal cavity, like other organs. Actually, the testes develop in the abdominal roof during the fetal period (near the kidneys), just as ovaries in females. Given the immense task of producing sperm (and therefore granting to forward our genes to future generations), we may wonder why are the testes out and less protected than other organs? Ovaries in female individuals, with very similar reproductive functions as the testes, remain inside the abdomen after they are formed.
So, why the testes need to be outside the abdomen? In order to understand this, we have to consider the process occurring inside the testes, a complex set of steps for sperm (spermatozoa) to form. This process is called spermatogenesis (genesis = generation; spermato = sperm). Many cells are implicated in this process, with a critical role undertaken by testis stem cells which give rise to sperm. This process in mammals (for reasons still unclear) requires a lower than the normal body temperature. Since a dog’s normal body temperature is around 101°F (about 38.5°C), the temperature for the testicular cells to properly work is near a maximum of 91.5°F (about 33°C). That is the reason why the testes must migrate out of the body cavity during development into their final adult destination, the modified skin pouch called scrotum (around the time of birth in most mammals). The whole process of migration is called testicular descent.
Curiously, in a few mammal species, the testes do not migrate outside of the body and stay and function normally inside the abdominal cavity. These mammals that y default have their testes inside the abdominal cavity (like dolphins, whales, and elephants, for instance), are more exceptions to the rule, and hold very efficient mechanisms to guarantee lower temperature in their testes, even though they are in the warmer inner body.

How testicular descent works?

The testes migrate from the inner abdominal cavity to the externally located scrotum (what we see externally in dogs and cats in a rearview) with the help of a special organ called gobernaculum which pulls the testes in their correct path. This gobernaculum organ is transitory and gradually disappears as the testis moves to its destination. This process is mediated by genes. The products of these genes (specific proteins) signal the events that must occur during testicular descent. In some dogs, several involved genes can be mutated (rendering very little or no protein at all produced), the process becomes impaired and one or both testes stop moving toward the scrotum and become cryptorchid.
In dogs, testis descent accelerates under the influence of androgens secreted by the fetal testis at the end of gestation. The testicle gets near the inguinal ring (a natural hole in the abdominal wall) at term and passes through the ring around day 5 after birth in dogs and the descent will be complete by six to eight weeks.

Faulty testicular descent mechanisms impair testis migration and one or both testes can become retained  inside or near the abdominal cavity. Normal testes in normal dogs travel outside of the abdominal cavity to a skin pouch called scrotum. Later in life the undescended  testis or testes can develop dangerous testicular cancer
Normal testes in normal dogs travel outside of the abdominal cavity (from a place right behind the kidneys) to a skin pouch called the scrotum. Not yet fully understood faulty mechanisms for testicular descent (“X”) impair testis migration and one or both testes can become retained inside or near the abdominal cavity. Later in life, the undescended testis or testes (cryptorchid) can develop dangerous testicular cancer.

Why testes fail to descend, and dogs and cats become cryptorchid?

By the time testicular descent should be complete (around day 60 after birth in most dog breeds), we can do a gentle palpation of the scrotal area to check that both testes are there. If you notice that there is just one testis present or both are missing, your dog can be considered cryptorchid. Besides environmental causes of cryptorchidism (there are way too many chemicals out there that can impair normal dog development), there is a genetic (hereditary) mechanism and the faulty genes involved can be transmitted to the offspring. For this reason, (but not the only reason, as you will discover below) dogs with cryptorchidism are often neutered by veterinarians.

Cryptorchidism or undescended hidden testes is a common problem in dogs affecting around 10% of dog populations. Faulty testicular descent mechanisms impair testis migration and one or both testes can become retained inside or near the abdominal cavity. Later in life the undescended testis or testes can develop dangerous testicular cancer. The causes of cryptorchidism are genetic and environmental. Many chemicals in the environment, some characterized as hormonal disruptors or chemicals that resemble reproductive and other hormones. (in drinking water, plastic containers, among others) can impair the process of testicular descent, commonly while in the mother’s uterus during pregnancy.
Cryptorchidism or undescended hidden testes is a common problem in dogs affecting around 10% of dog populations. Faulty testicular descent mechanisms impair testis migration and one or both testes can become retained inside or near the abdominal cavity. Later in life the undescended testis or testes can develop dangerous testicular cancer types. The causes of cryptorchidism are genetic and environmental. Many chemicals in the environment, some characterized as hormonal disruptors or chemicals that resemble reproductive and other hormones (in drinking water, plastic containers, among others) can impair the process of testicular descent during pregnancy.

If a cryptorchid testis is not extracted, the undescended testis or testes may develop dangerous testicular cancer types later in life (there is evidence that the temperature of the abdominal cavity can produce this).
Besides genetics, cryptorchidism can be triggered by environmental chemicals. Some of these chemicals are characterized as hormonal disruptors (chemicals that mimic the reproductive and other hormones of dogs and cats). These hormonal disruptors can be commonly found nowadays in drinking water, plastic containers, among others, and may impair the process of testicular descent in dogs and cat fetuses while in the mother’s womb during pregnancy.

Remember: When cryptorchidism is present, the probability of testicular cancer in dogs and cats is very high

Can dogs with undescended (cryptorchid) breed?

Monorchid dogs (with one descended testis and the other undescended) can technically breed. The descended (normal) testis will make up for the undescended one, producing enough sperm to impregnate a female dog. Also, technically speaking, just one sperm taken from the descended testis would be enough to perform an artificial reproduction procedure called ICSI (intracytoplasmatic sperm injection) and generate dog embryos and puppies through special procedures. But the thing is that undescended testes in dogs have a genetic origin that can be transmitted to future generations.

What happens if we don’t do anything about a case of cryptorchid testes?

Besides transmitting the condition to future generations, we already mentioned that, dangerously enough, the retained testis can develop very malignant testicular tumors as the dog ages (in the worst-case scenario).
In cats, cryptorchidism also generates a big risk for testicular cancer.
For these reasons it is strongly advised that dogs and cats be neutered (particularly the retained testis taken off). In humans, pediatricians that detect cryptorchid testes in children will recommend performing an extraction surgery as early as possible, if not immediately upon diagnosis in most cases (even in babies).
If we don’t do anything and we are lucky enough our dog or cat won’t develop a tumor, our pet has a high chance to become infertile. The reason for this is that undescended testis will probably carry only immature germ stem cells and sperm won’t form later in life. Because of the higher temperature within the body, where the retained testis is located, these testicular stem cells will not be able to divide and produce sperm (or worse, let’s stress this, will go ugly later on and produce testicular tumors). In the meantime, the cryptorchid testis will still be able to produce testosterone. In the worst scenario, if both testes are retained, the dog will be unfertile, but still produce androgens like testosterone to maintain male dog sexual behavior and sexual characteristics, just as it happens in normal dogs (testosterone drives the male dog or cat to have their normal male behavior).

What about cats and cryptorchidism?

Some facts about cryptorchidism in cats:

  • Testicular descent in cats occurs usually by month 2, but no later than 6 month of age.
  • Cryptorchidism is more common in Persian breed cats (near 40% of affected cats in some reports).
  • Cryptorchidism is heritable in cats (as in dogs) with several genes involved. Because of this, castration of the affected cat is recommended.
  • Testicular cancer in cats is less common than in dogs.
  • Cryptorchid cats should not be bred.
  • Cats with retained testes will keep male behaviors such as marking and spraying, and aggressive behavior toward other cats.

What should we do about undescended testes (cryptorchidism) in our dogs and cats?

Once we notice our dog or cat is lacking one or both testes inside the scrotum, we should program a visit to our favorite Vet as soon as possible. If only one testis is undescended one possibility is to extract this undescended testis and keep the other. The remaining normal testis can keep the dog or cat with functioning sexual hormones and even fertile, but as we said before, these pets should not be bred to avoid transmitting the defective genes to their offspring so that the problem won’t become perpetuated in time and space in dog and cat populations.

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