Wed, 01/12/2022 - 11:52pm

Retained Testicles

When nature doesn't provide a matching pair

My veterinarian says my puppy only has one testicle. What does that mean?


Male dogs should have two testicles of equal size. The testes develop near the kidneys within the abdomen and normally descend into the scrotum by the time the puppy is two months old. Descent may occur later in some breeds, but rarely after six months of age.

Cryptorchidism is the term for the condition where one or both of the testicles are not in their proper position. Monorchidism is the total absence of one testicle, meaning it never grew at all, and anorchidism is the total absence of both testicles.

Studies have shown the testicle moves away from its original position near the kidney through the inguinal ring in the groin and out of the abdomen by the fifth day of age. It should be between the inguinal ring and the scrotum by day 15, and in place in the scrotum by day 40. The puppy is assumed to be cryptorchid if one or both testes cannot be palpated in the scrotum after four months of age.

Cryptorchidism is related to gubernaculum development. The gubernaculum is a fibrous band of tissue that connects the fetal testes to the developing scrotum. If the gubernaculum fails to develop, the testicle remains in the abdomen. If the gubernaculum develops abnormally, the testicle may reach the inguinal ring and start along the inguinal canal, but will not reach the scrotum.

Though Toy breeds are at higher risk, cryptorchidism occurs in all breeds. Approximately 75 percent of cases involve only one retained testicle, while the remaining 25 percent involve failure of both testicles to descend. The left testicle usually descends first, and the right testicle is more than twice as likely to be retained as the left.

This condition affects approximately 5 percent of all dogs. It appears to be inherited since it is commonly seen in families and pedigrees with both the sire and dam implicated, but the exact mechanism is not fully understood. It is thought to be genetically passed on as a sex-limited chromosomal recessive trait: Both the sire and dam carry the trait, but only males exhibit the trait.


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


In most cases of cryptorchidism, the testicle has not passed through the inguinal ring and is still in the abdomen. When a testicle is located within the abdominal cavity after the first few weeks of life, it will likely remain there because of closure of the internal inguinal ring.

If the testicle starts its descent and gets through the inguinal ring, it may be located in the inguinal canal, which is the passage through the abdominal wall into the genital region. Sometimes the testicle will be located just below the skin in the groin between the inguinal ring and the scrotum.

Testicles that are actually in the scrotum or just above the scrotum may be difficult to palpate if they are small in size or the puppy is too fat. If the testicle is in the inguinal canal, it may be able to be palpated, or felt, during a physical examination. Testes that are retained in the abdomen are not able to be palpated unless they are enlarged.

If the undescended testicle is in the abdomen, it will not contain sperm, since the higher core body temperature suppresses sperm development. However, retained testicles will still produce testosterone.


Is there a way to pinpoint the location of a missing testicle?


Radiographs of the abdomen may show a mass effect if the retained testis is enlarged. Ultrasonic examination may be more effective. The testicle appears as an oval structure somewhere between the kidney and the inguinal ring. Advanced imaging such as computed tomography (CT) or magnetic resonance imaging (MRI) can be used to detect abdominal testicles.

Testosterone measurement is another method used to determine whether testes are present. Since testosterone is released in a sporadic manner, a low blood level of testosterone does not confirm the absence of testicles. However, high levels of testosterone suggest testicles are present somewhere. Blood levels of testosterone may be lower than normal in dogs with both testes retained in the abdomen.

Hormone-stimulation tests such as gonadotrophin-releasing hormone (GnRH) and human chorionic gonadotrophin (HCG) stimulation tests are the best way to diagnose retained testes. Both GnRH and HCG cause testosterone release. Although the retained testicle is not capable of producing sperm, it can produce testosterone.

Testosterone does not change after administration of GnRH or HCG in a castrated or anorchid dog, but it will increase by at least double in a cryptorchid dog. GnRH stimulation is the preferred test since it is less likely to cause pain at the injection site and the post-stimulation blood sample is collected sooner, making it a faster test to perform.

Some retained testicles are only found during exploratory surgery of the abdomen and/or inguinal canal. If the testes are retained in the abdomen for a long period of time, they may develop testicular, or spermatic cord, torsion where the testicle twists on itself. Signs of this are sudden and severe abdominal pain. More frequently, a retained testicle will become cancerous. The symptoms associated with testicular cancer depend on the specific type of cancer.


What is the treatment for cryptorchidism?


No specific therapy has been shown to be effective in coaxing a retained testicle to descend. Because of the increased potential for testicular torsion or cancer, surgical removal of the testicles, both descended and undescended, is the treatment of choice. The risk of cancer increases dramatically after five years of age, so neutering is recommended as soon as the dog reaches maturity.

If only one testicle is retained, the dog will have two incisions – one for extraction of each testicle, scrotal and then abdominal or inguinal. If both testicles are in their respective inguinal canals, there will also be two incisions – one in each groin area. When both testes are in the abdomen, a single abdominal incision, similar to a spay surgery, allows access to both.

The American Veterinary Medical Association states that surgical repair or surgical placement of prosthetic material in the scrotum to represent the cryptorchid testicle (one example of this is Neuticles) for purposes of concealing the genetic defect is unethical.

Several veterinarians recommend the use of the Chinese herb epimedium, as well as acupuncture to help get a retained testicle down. Another suggestion for a testicle that is not far from the scrotum included gentle traction massage repeated several times a day. Although this technique can be somewhat uncomfortable to the puppy, it has been reported to be effective in some cases.



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