Cryptorchidism

TL;DR. Cryptorchidism is a common hereditary condition where one or both testicles fail to descend into the scrotum, requiring surgical removal to prevent serious health complications like cancer and testicular twisting.

In normal development, the testicles migrate from near the kidneys down into the scrotum.

What is it?

Cryptorchidism is a common congenital reproductive defect in male dogs and cats where one or both testicles fail to descend into the scrotum by the time the animal reaches puberty. During normal fetal development, the testicles form near the kidneys (at the caudal renal pole). As the pet grows, a specialized ligament pulls the testicles down through the abdomen, through the inguinal canal in the groin, and finally into the scrotum.

In healthy puppies and kittens, this descent is typically complete by 6 to 16 weeks of age. However, in cryptorchid animals, this migration process fails. The retained testicle can become trapped anywhere along this path: deep within the abdominal cavity near the kidneys, inside the inguinal canal, or in the subcutaneous tissue of the groin just under the skin.

This condition is more than a cosmetic issue. The internal temperature of the abdomen is significantly higher than the temperature inside the scrotum. This chronic heat exposure prevents normal sperm development, leading to infertility or reduced fertility. More importantly, the retained tissue is highly prone to developing life-threatening complications, including testicular cancer and a painful twisting of the blood supply known as testicular torsion.

Causes & risk factors

Cryptorchidism is primarily a hereditary and congenital defect, meaning animals are born with it due to genetic factors passed down from their parents. Because it is a genetic trait, affected animals should never be used for breeding.

While the condition can occur in any male dog or cat, it is significantly more common in dogs than in cats. Certain breeds have a much higher genetic predisposition to the condition. For example, the Dachshund is highly predisposed, with research indicating the condition is inherited as an autosomal recessive trait in this breed. Small and toy breed dogs also experience a higher incidence of retained testicles compared to large breeds.

Signs to watch for

In many cases, a pet with cryptorchidism will show no outward signs of illness. However, there are several key physical and behavioral signs to watch for:

• Absence of one or both testes in the scrotum (cardinal): By the time your pet is 4 to 6 months old, both testicles should be easily felt in the scrotum. If one or both are missing, your pet is cryptorchid.
• Reduced fertility in unilateral cases (common): If only one testicle is retained, the descended testicle can still produce sperm, but overall fertility is typically reduced.
• Infertility in bilateral cases (common): If both testicles are retained inside the body, the heat will prevent sperm production entirely, rendering the pet sterile.
• Normal libido and secondary sex characteristics (common): Even though the retained testicle cannot produce viable sperm, it still produces testosterone. Your pet will still exhibit male behaviors, such as marking, mounting, and intact male physical characteristics.
• Prominent prostate gland (occasional): Continued testosterone production can lead to prostate enlargement over time.
• Testicular neoplasia (occasional): Retained testicles are significantly more likely to develop tumors, such as Sertoli cell tumors and seminomas. This can cause abdominal swelling, skin changes, or feminization syndrome (where the male pet develops enlarged nipples or attracts other male dogs due to estrogen production).
• Testicular torsion (occasional): This is a sudden, life-threatening emergency where the retained testicle twists on its blood supply, causing severe, acute abdominal pain, vomiting, and lethargy.

An empty scrotal sac and a small bulge in the groin are common physical signs of a retained testicle.

How vets diagnose it

Your vet will begin with a thorough physical examination and palpation. If the retained testicle is located in the groin (subcutaneous tissue), your vet can often feel it during a routine puppy or kitten exam. However, if the testicle is located deep within the abdomen, palpation alone is rarely sufficient.

To locate an abdominal testicle, ultrasonography is the gold standard diagnostic tool. Ultrasound allows the vet to visualize the internal structures of the abdomen with high precision. As noted in a leading textbook on small animal ultrasound:

"Ultrasound has a high accuracy in diagnosis of testicular and/or scrotal disorders in dogs... Cryptorchid testicles are usually small and hypoechoic, but have normal architecture with a central hyperechoic mediastinum"

Ultrasound is the gold standard tool for locating a testicle retained deep inside the abdomen.

If your pet's surgical history is unknown—such as a rescued adult dog or cat with no visible testicles—your vet may recommend hormonal testing. A human chorionic gonadotropin (HCG) stimulation test measures testosterone levels before and after an injection. If testosterone levels rise after the injection, it confirms that active testicular tissue is still present inside the body, indicating the pet is cryptorchid rather than previously neutered.

Treatment options

The definitive and highly recommended treatment for cryptorchidism is surgical removal of both testicles, a procedure known as a bilateral orchiectomy (neutering).

During this surgery, the vet will remove the normally descended testicle as well as the retained testicle. If the retained testicle is in the abdomen, the surgery is more complex than a standard neuter, requiring an abdominal incision similar to a female spay. The surgeon must carefully locate the retained organ, isolate the blood vessels, and secure them. A standard veterinary surgical manual describes the precise technique used to secure the delicate tissues:

"Any fat investing the spermatic cord is stripped from the cord and, in a proximal position, two Halstead mosquito forceps are placed across the spermatic cord. As the proximal forceps is removed a ligature of absorbable suture material is tied tightly in the crush mark."

Some owners ask if the retained testicle can simply be surgically pulled down and anchored into the scrotum (a procedure called orchiopexy). In veterinary medicine, this is considered highly unethical and medically contraindicated. As a leading veterinary internal medicine reference states:

"Orchiopexy is also considered unethical. In humans, the increased incidence of neoplasia in the formerly intraabdominal cryptorchid testis persists post orchiopexy, making the procedure contraindicated medically in veterinary patients as well as being unethical."

Because anchoring the testicle does not lower the elevated risk of cancer, and because it could allow a genetically defective animal to be bred or shown, professional standards strictly prohibit this procedure.

In very young puppies (under 16 weeks), some veterinarians may discuss temporary hormonal therapies, such as Chorionic Gonadotropin (HCG) or Testosterone, to attempt to stimulate natural descent. However, these therapies have low success rates, are rarely recommended, and must never be used to bypass the genetic implications of the condition for breeding stock.

Prognosis

The long-term prognosis for pets with cryptorchidism is excellent, provided they undergo surgical removal of both testicles. Once the surgery is complete, the risk of testicular cancer and testicular torsion is completely eliminated. Your pet will recover fully within 10 to 14 days and can expect to live a normal, healthy, and active life.

If the surgery is not performed, the prognosis is guarded due to the high likelihood of tumor development and the sudden risk of life-threatening testicular torsion as the pet ages.

Prevention

Because cryptorchidism is a congenital and hereditary defect, there is no lifestyle change, diet, or environmental intervention that can prevent it from occurring in an individual animal.

The only effective prevention is genetic management. Breeders must remove affected dogs and cats from their breeding programs. Because the condition is often carried silently by females or non-affected males (especially in breeds like the Dachshund where it is inherited as an autosomal recessive trait), close relatives of affected animals should also be evaluated carefully before breeding.

When to call your vet

You should schedule a veterinary visit if your male puppy or kitten is over 16 weeks of age and you cannot feel two distinct testicles in the scrotum.

If your pet is a known cryptorchid and has not yet undergone surgery, you must monitor them closely. Seek emergency veterinary care immediately if your pet exhibits any of the following signs, which can indicate life-threatening testicular torsion or advanced tumor complications:

• Sudden, severe abdominal pain (whining, guarding the belly)
• Persistent vomiting or loss of appetite
• Extreme lethargy or weakness
• A sudden, painful swelling in the groin area
• Symmetrical hair loss, skin darkening, or breast development in a male pet

For specific breeds

Dachshund

Dachshunds carry a well-documented genetic predisposition to cryptorchidism. In this breed, the condition is inherited as an autosomal recessive trait. This means an individual Dachshund must inherit the defective gene from both parents to physically display the condition. Parents of an affected Dachshund are confirmed carriers of the gene, even if they appear completely normal. If you own a Dachshund, ensure your vet carefully checks for bilateral testicular descent at every puppy check-up.

Sources

• Small Animal Internal Medicine, 5th Edition, p. 978.
• Current Techniques in Small Animal Surgery, 5th Edition, p. 565.
• Atlas of Small Animal Ultrasonography, 2nd Edition, p. 451.