As a dog lover and veterinarian, one of the most common congenital defects I see in practice is cryptorchidism. This is where one or both of a male dog‘s testicles fail to descend into the scrotum. For owners, it can be worrying to discover their dog is missing a testicle. But rest assured, with appropriate treatment, your dog can still live a full, healthy life. In this article, I‘ll dive into the details of cryptorchidism in dogs so you can be an informed advocate for your furry family member.
Normal Testicular Development
First, it‘s important to understand how the testicles normally descend during development. A male puppy‘s testicles actually start out in the abdomen near the kidneys. During the last few weeks of gestation, the testicles migrate through the inguinal canals, which are passages through the abdominal wall, and into the scrotum. This is triggered by a complex cascade of hormones.
Normally, both testicles are palpable in the scrotum by 6-8 weeks of age in puppies. They may be slightly difficult to feel in some puppies up until 6 months old as they go through phases where the testicles are smaller or larger. But by 6 months old, it should be obvious that both testicles are fully descended into the scrotum.
What Is Cryptorchidism?
Cryptorchidism is the failure of one or both testicles to descend into the scrotum. It comes from the Greek words "crypto" meaning hidden and "orchid" meaning testicle. The retained testicle can be in one of three locations:
- Abdominal cryptorchidism: The testicle remains in the abdomen
- Inguinal cryptorchidism: The testicle is in the inguinal canal
- Subcutaneous cryptorchidism: The testicle is under the skin in the groin area
We classify cryptorchidism as unilateral, meaning one testicle is retained, or bilateral, where both are retained. Unilateral is more common, occurring in about 75% of cases.
Prevalence
Cryptorchidism is one of the most common congenital defects in dogs. Studies estimate it occurs in 1-3% of the dog population. However, this number is likely higher as many cases go undiagnosed if dogs are neutered at a young age before the absence of a testicle is noted.
Certain breeds are predisposed to cryptorchidism. Toy breeds and brachycephalic (flat-faced) breeds tend to have the highest incidence. According to a study in Veterinary Medicine: Research and Reports, the breeds with the highest prevalence include:
| Breed | Prevalence |
|---|---|
| Toy Poodle | 8.8% |
| Pomeranian | 7.4% |
| Yorkshire Terrier | 6.9% |
| Miniature Schnauzer | 5.2% |
| Maltese | 4.7% |
| Chihuahua | 4.5% |
| Pekingese | 4.3% |
| Boxer | 3.9% |
| French Bulldog | 3.6% |
| Bulldog | 3.4% |
However, it‘s important to note that cryptorchidism can occur in any breed, including mixed breeds. Purebred dogs from closely inbred lines tend to be at higher risk.
Causes
Cryptorchidism is considered an inherited disorder. The exact genes involved have not been identified, but we know it has a complex, polygenic mode of inheritance. This means it involves multiple genes rather than a single gene. It is also sex-limited, meaning only males are affected, and autosomal recessive, meaning a puppy must inherit the genes from both parents to express the trait.
Although the exact cause is unknown, we know there is a strong genetic component. This is why it is not recommended to breed any dog with cryptorchidism, even if they are unilaterally cryptorchid and capable of reproducing. Doing so propagates these deleterious genes in the breeding pool.
Environmental and maternal factors may also play a role, as cryptorchidism rates are higher in litters from older dams. However, genetics are still the primary cause.
Diagnosis
Cryptorchidism is most often diagnosed during a routine veterinary physical exam. If one or both testicles are not palpable in the scrotum by 6 months of age, cryptorchidism is confirmed.
On exam, veterinarians carefully palpate the scrotum, inguinal area, and groin to feel for the missing testicle(s). In some cases, the retained testicle can be difficult to locate, especially if it is in the abdomen. According to the Merck Veterinary Manual, abdominal cryptorchidism accounts for about 50% of cases, inguinal cryptorchidism 45%, and subcutaneous cryptorchidism just 5%.
Imaging techniques can also be used to locate retained testicles that aren‘t readily palpable. Ultrasound is most commonly used. It allows visualization of the testicle and associated structures. However, even ultrasound may not locate a small intra-abdominal testicle. Other imaging options include CT and MRI, although these are less commonly utilized.
Hormone testing can also provide valuable information, especially in bilaterally cryptorchid dogs. Baseline testosterone levels or hormonal stimulation tests can help differentiate between bilaterally cryptorchid dogs, which still produce testosterone, and castrated dogs that do not.
Fertility and Behavioral Impacts
The scrotum functions to keep the testicles at a temperature slightly lower than the core body temperature. This is essential for normal sperm production and maturation. When a testicle is retained in the abdomen or inguinal canal, it is exposed to a higher temperature, disrupting spermatogenesis.
Therefore, bilaterally cryptorchid dogs are sterile. The retained testicles simply cannot produce viable sperm at core body temperature. Unilateral cryptorchids are often still fertile if the scrotal testicle is normal. However, the sperm numbers and quality may be reduced compared to normal dogs.
From a behavioral standpoint, cryptorchid dogs are identical to intact males. Even retained testicles produce normal amounts of testosterone. Thus, cryptorchid dogs will still exhibit marking, roaming, humping, and aggression if not neutered. Testosterone production is not impacted by the location of the testicle.
Complications
There are two major potential complications of cryptorchidism: spermatic cord torsion and testicular neoplasia.
Spermatic cord torsion refers to twisting of the spermatic cord – the bundle of tissue containing the vas deferens, blood supply, nerves, and other supportive tissues attached to the testicle. If this twists on itself, it cuts off the blood supply, leading to severe pain and eventual testicular necrosis (tissue death). Although rare, occurring in less than 1% of cryptorchid dogs, it is considered a medical emergency. Immediate surgical removal of the testicle is required to relieve pain and prevent sepsis.
The more common and serious complication is development of a testicular tumor. Cryptorchid dogs are an alarming 13.6 times more likely to develop testicular neoplasia compared to normal dogs according to the Journal of the American Animal Hospital Association. The increased risk is likely due to the higher temperature exposure and disrupted spermatogenesis.
The most common testicular tumor in cryptorchid dogs is the Sertoli cell tumor, followed by the seminoma. These tumors often develop later in life, with the average age being 10 years old. Clinical signs depend on the tumor type but may include asymmetric enlargement of the retained testicle, abdominal pain, lethargy, and feminization (if an estrogen-secreting Sertoli cell tumor).
Treatment
The treatment of choice for cryptorchidism is surgical removal of both testicles, also known as neuter or castration. For the cryptorchid testicle, an incision is made in the region where it is located (inguinal or abdominal). The spermatic cord is ligated and the testicle is removed. The descended testicle is removed via a pre-scrotal incision as in a standard neuter.
Castration of cryptorchid dogs is a bit more involved than a routine neuter. It requires more time and surgical skill to locate the retained testicle. Abdominal exploration may be required for those high in the abdomen that aren‘t palpable in the inguinal region. However, complication rates are still low with an experienced veterinary surgeon.
I strongly advocate for neutering of all cryptorchid dogs before one year of age. According to a study in the Journal of the American Veterinary Medical Association, the average age at diagnosis is 8 months and average age at neuter is just over 1 year. Waiting past a year allows more time for testicular tumors to potentially develop.
There is no advantage to leaving a retained testicle as it does not produce sperm and predisposes the dog to cancer. Furthermore, the surgery becomes more difficult in older dogs. In one study, cryptorchid dogs over 4 years of age had twice the rate of surgical complications compared to those under 4 years old.
Recovery from neuter surgery is similar to a routine castration. An Elizabethan collar is worn to prevent licking at the incision. Activity is restricted for 2 weeks while the incision heals. Pain is well-controlled with appropriate medications. In a study of 73 cryptorchid dogs undergoing surgery, 100% recovered without incident.
Prognosis
The prognosis for cryptorchid dogs is excellent if diagnosed and neutered early in life before complications develop. Once the retained testicle(s) are removed, there is no increased risk of future reproductive issues.
If a tumor develops in a retained testicle, the prognosis depends on the tumor type. Sertoli cell tumors and seminomas have a good prognosis with an 86-100% 1-year survival rate after surgical removal. However, other tumor types like Leydig cell tumors and embryonal carcinomas are more aggressive with a 10-20% metastatic rate.
Frequently Asked Questions
Q: Can a retained testicle ever descend on its own?
A: No, if the testicle has not descended by 6 months of age, it is considered permanently cryptorchid. Waiting will not result in normal descent.
Q: Is cryptorchidism painful for dogs?
A: No, cryptorchidism itself is not painful. Dogs will not show any signs of discomfort. Pain only occurs if a complication like spermatic cord torsion or tumor develops.
Q: Can a dog still breed if he is unilaterally cryptorchid?
A: It‘s possible since the scrotal testicle may produce viable sperm. However, cryptorchid dogs should never be intentionally bred since it is a hereditary condition.
Q: How much does surgical correction of cryptorchidism cost?
A: The average cost of a cryptorchid neuter is around $800. However, this varies widely based on location, the dog‘s size, and whether a board-certified surgeon is required. Pre-surgical bloodwork and imaging also add to the total cost.
Q: Can the surgery be done laparoscopically?
A: Yes, laparoscopic cryptorchidectomy is possible. It is a less invasive approach using a camera and instruments placed through small incisions in the abdomen. However, it requires specialized equipment and training, so availability may be limited.
Q: What happens if the retained testicle cannot be found during surgery?
A: In the hands of an experienced veterinarian, 96% of retained testicles are successfully located. If it truly cannot be found, hormone testing is used to confirm the dog is now castrated. Occasionally, a second surgery is needed.
Q: How can I prevent my dog from developing cryptorchidism?
A: Since cryptorchidism is a hereditary defect, the best prevention is avoiding breeding dogs with a known history in their lineage. All breeding dogs should have a thorough physical exam to ensure two descended testicles before being bred.
Conclusion
Cryptorchidism is a common congenital abnormality where one or both testicles fail to descend into the scrotum. It may seem like a minor anatomic quirk, but it actually predisposes the dog to some serious health risks, namely testicular cancer.
The good news is that cryptorchidism is easily corrected with surgery. And if done early, the prognosis is excellent. If you have any concerns about your dog‘s testicles, don‘t hesitate to talk to your veterinarian. They can confirm if your dog is cryptorchid and discuss the best treatment plan.
Remember, your dog can‘t advocate for himself, so it‘s up to you to prioritize his health. With appropriate treatment, your cryptorchid dog will go on to live a normal, happy life by your side!
References
- Yates D et al. Incidence of and risk factors for orchidectomy and spermatic cord torsion in a UK dog population under primary veterinary care. Vet Rec. 2018.
- Birchard SJ and Nappier M. Cryptorchidism. Compend Contin Educ Vet. 2008.
- Millis DL et al. Cryptorchidism in dogs: 73 cases (1980-1989). JAVMA. 1992.
- Gurel A et al. Sertoli cell tumours in dog: 37 cases. Ank Univ Vet Fak Derg. 2017.
- Duffy DJ and Moore GE. Spermatic cord torsion in dogs: 5 cases. Vet Rec Case Rep. 2016.
