Cryptorchidism in dogs: diagnosis, risks, treatment

What is cryptorchidism in dogs?

Cryptorchidism (Greek kryptos = hidden, orchis = testicle) is the technical term for an undescended testicle in dogs — the complete or partial failure of the physiological descent of the testicle into the scrotum. One or both testicles remain either in the abdominal cavity (abdominal cryptorchidism) or in the inguinal canal (inguinal cryptorchidism) instead of descending into the scrotum.

The term is often used synonymously with undescended testicle, but it is the clinical and medical designation. Cryptorchidism is the most common congenital genital anomaly in dogs and has significant health and breeding-related consequences.

Background + scientific classification

Yates et al. (2011, Breed Predispositions to Disease in Dogs and Cats, PubMed 21498416) document breed predispositions for cryptorchidism: Chihuahuas, Toy Poodles, Pomeranians, Boxers, Pekingese, German Shepherds, and Yorkshire Terriers are particularly commonly affected. Depending on the breed and study, the incidence ranges from 0.7% to 13% of all male dogs. Unilateral cryptorchidism is significantly more common than bilateral cryptorchidism; the right testicle is affected more often than the left.

Liao et al. (2009, Veterinary and Comparative Oncology, PubMed 19743399) analyzed the c-KIT mutation-associated development of seminomas in cryptorchid dogs: retained testicles have an approximately 9-fold increased risk of developing a testicular tumor compared with normally positioned testicles. Sertoli cell tumors and seminomas in particular develop in retained testicles. The higher body temperature in the abdominal cavity or inguinal canal promotes malignant transformation. Castration — including in dogs with unilateral cryptorchidism — eliminates this risk completely.

Hayes (1986, JSAP, PubMed 3701507) analyzed 5,009 cryptorchid dogs in a historical reference dataset: cryptorchidism has a strong genetic component — affected males, as well as their sons and sires, show an increased incidence in offspring. Cryptorchid males and carrier females should not be used for breeding — a principle that is now widely recognized in modern breeding regulations.

Vitomalia position

Cryptorchidism is an inherited disorder that clearly requires action: neutering with removal of both testicles — including the correctly positioned one — is the clear recommendation for health and breeding-related reasons. Cryptorchid male dogs should not be used for breeding. This also includes seemingly fertile unilateral cryptorchid male dogs.

When does cryptorchidism become relevant?

• Routine puppy examination: from 6–8 weeks, use bimanual palpation to check both testicles in the scrotum
• Diagnosis by 6 months of age: both testicles should be in the scrotum by then
• If a testicle is missing from the scrotum: localization by ultrasound (groin/abdomen)
• Neutering surgery: the cryptorchid testicle must be surgically located and removed
• Breeding planning: exclude cryptorchid male dogs and their relatives from breeding

Practical application

Cryptorchidism — clinical classification:

Type	Localization	Frequency	Surgical complexity
Unilateral inguinal	Inguinal canal	Most common type	Low
Unilateral abdominal	Abdominal cavity	Common	Moderate
Bilateral	Bilateral/unilateral	Less common	Higher

Diagnostics: 1. Palpation: from 6–8 weeks, repeated until 6 months of age 2. Ultrasound: localization of the retained testicle (inguinal canal or abdomen) 3. hCG stimulation test: when it is unclear whether the dog has been neutered or has a cryptorchid abdominal testicle 4. Histopathology after surgery: ruling out tumors

Surgical approach: - Inguinal testicle: usually accessible via the groin area - Abdominal testicle: laparoscopy or laparotomy - Always remove both testicles (including the scrotal one in unilateral cryptorchidism)

Common mistakes & myths

• “One testicle is in the scrotum, so everything is fine.” Unilateral cryptorchidism — the retained testicle remains a tumor risk. Neutering with removal of both testicles is the clear recommendation.
• “Cryptorchidism can still develop up to the first year of life.” Both testicles should be in the scrotum by 6 months of age at the latest. Beyond this point, spontaneous descent is unlikely and veterinary assessment is indicated.
• “Cryptorchid male dogs are infertile.” Unilateral cryptorchid male dogs can often be fertile — the remaining scrotal testicle produces sperm. However, that does not mean breeding is responsible: the inherited disorder can be passed on.

Scientific Status 2026

The genetic basis of cryptorchidism in dogs is the subject of active research; a single major gene defect has not yet been identified — polygenic involvement is suspected. Laparoscopic surgical techniques have made abdominal cryptorchidism significantly gentler for patients. DNA tests for cryptorchidism carriers are in development for some breeds, but are not yet widely available.

Frequently Asked Questions

When should both testicles be in the scrotum in a male dog?

Both testicles should be palpable in the scrotum by the age of 6 months at the latest. They are palpated during the first puppy examination (6–8 weeks). If one testicle is not in the scrotum after 6 months, veterinary diagnostics and advice on neutering are recommended.

Does a cryptorchid dog need to be neutered?

Clear recommendation: yes. The retained testicle has a 9-fold increased risk of tumor development and cannot be monitored by palpation. In unilateral cryptorchidism: neutering of both testicles — even if one testicle is correctly positioned, as the male could otherwise still be used for breeding.

Is cryptorchidism hereditary?

Yes — cryptorchidism has a clear genetic component. Affected males, their fathers, and their sons show an increased incidence. Cryptorchid males and known carriers should be excluded from breeding — as is stipulated in most breeding regulations of reputable associations.

Related Terms

• Cryptorchidism in Dogs
• Neutering in Dogs
• Testicular Tumor in Dogs
• Hereditary Diseases in Dogs
• Reproduction in Dogs

Sources & Further Reading

1. Yates, D., & Hayes, G. (2011). Breed Predispositions to Disease in Dogs and Cats (2nd ed.). Wiley-Blackwell. https://pubmed.ncbi.nlm.nih.gov/21498416/

2. Liao, A. T., Chu, P. Y., Yeh, L. S., Lin, C. T., & Liu, C. H. (2009). A 12-year retrospective study of canine testicular tumors. Veterinary and Comparative Oncology, 7(3), 229–238. https://pubmed.ncbi.nlm.nih.gov/19743399/

3. Hayes, H. M., Jr., Pendergrass, T. W. (1986). Canine testicular tumors: Epidemiological features of 410 dogs. Journal of Small Animal Practice, 27(10), 637–649. https://pubmed.ncbi.nlm.nih.gov/3701507/