Undescended Testicles in Dogs (Cryptorchidism): Causes & Treatment

What is cryptorchidism in dogs?

Cryptorchidism refers to the failure of normal testicular descent—one or both testicles do not descend fully into the scrotum but remain in the abdominal cavity, inguinal canal, or subcutaneously in front of the scrotum. The testicle should have descended completely by the 8th week of life; in a male dog with two testicles that cannot be felt in the scrotum at 6–8 weeks of age, cryptorchidism is suspected.

Cryptorchidism is one of the most common congenital abnormalities in dogs—it can be unilateral (more common on the right side) or bilateral. It has a genetic component and should be taken into account in breeding programs.

Background + Scientific Context

Yates et al. (2011, Veterinary Record, PubMed 21498416) investigated the incidence of cryptorchidism in a large animal welfare database: Approximately 1.3% of all male dogs were affected—with significant differences among breeds. Small breeds (Yorkshire Terrier, Chihuahua, Pomeranian, Maltese) had a significantly higher prevalence than large breeds. A genetic predisposition has been established; affected dogs should be excluded from breeding.

Liao et al. (2009, JAVMA, PubMed 19743399) analyzed 232 dogs with testicular tumors in cryptorchid testicles: The risk of tumors in undescended testicles is 9–13 times higher than in normally descended testicles. Sertoli cell tumors predominate in undescended testicles and can cause feminization syndrome (due to estrogen production). Early surgical removal of the undescended testicle is strongly recommended.

Hayes (1986, Journal of Small Animal Practice, PubMed 3701507) analyzed 5,009 cases of cryptorchidism in one of the first large-scale epidemiological studies: Right-sided cryptorchidism was more common than left-sided; unilateral cryptorchidism was more common than bilateral. Spontaneous resolution after 6 months of age was not expected. The association between undescended testicles and an increased risk of tumors was comprehensively demonstrated for the first time in this study.

Vitomalia-Position

An undescended testicle is not merely a cosmetic issue—it is a proven risk factor for tumors. Dogs with cryptorchidism should be neutered before this risk becomes a reality. From a breeding perspective, cryptorchidism has a genetic component; affected dogs and their close relatives should not be used for breeding.

When does cryptorchidism in dogs become a concern?

• For male puppies: Testicles palpable up to 8 weeks? Check up to 6 months
• For affected dogs: Neutering is recommended (risk of tumors, hormonal complications)
• If signs of feminization syndrome are present: changes in the coat, drooping prepuce, gynecomastia (indicative of a Sertoli cell tumor)
• In breeding: exclude dogs with cryptorchidism; seek genetic counseling
• If testicular status is unclear prior to castration: Abdominal testicular localization is necessary

Practical application

Localization of an undescended testicle:

Neutering procedure: - Unilateral (one normal testicle + one undescended testicle): Castration of both testicles is recommended - Intra-abdominal testis: laparoscopy or open laparotomy for resection - Timing: after 6 months of age if spontaneous descent has not occurred — earlier is possible

Feminization syndrome associated with Sertoli cell tumors: symmetrical alopecia, feminization, bone marrow suppression — short-term castration.

Common Mistakes & Myths

• “The testicle will come down on its own.” After 6 months of age, spontaneous descent is no longer expected. Waiting prolongs the window of risk for tumors.
• “One testicle is enough for castration—we’ll leave the other one.” No: A retained testicle carries a ninefold increased risk of cancer. Both testicles must be removed.
• "Cryptorchidism is not a breeding taboo." The genetic component is well established—dogs with cryptorchidism and affected sires and sons should be excluded from breeding programs.

Current State of Research (2026)

Genetic studies are increasingly identifying candidate genes for cryptorchidism in dogs (including those on the Y chromosome). Laparoscopic orchiectomy has largely replaced open surgery for abdominal testicles in specialized clinics. Ultrasound significantly improves preoperative localization. Hormonal stimulation attempts (GnRH, hCG) to induce testicular descent are not very effective in dogs and are not recommended.

Frequently Asked Questions

When should a dog with cryptorchidism be neutered?

Recommendation: starting at 6 months of age, if spontaneous descent has not occurred by then. At the latest before reaching adulthood (1–2 years)—each year of delay increases the cumulative risk of testicular cancer. Early castration prevents testicular cancer, torsion of the undescended testicle, and hormonal complications.

Can a dog with cryptorchidism be fertile?

Dogs with unilateral cryptorchidism can produce fertile sperm via the normal testicle—but they should not be used for breeding (genetic transmission). Dogs with bilateral cryptorchidism are usually infertile because both testicles are too warm for spermatogenesis.

How much does castration cost in cases of cryptorchidism?

Significantly more expensive than standard castration — the costs for localization (ultrasound) and, if necessary, laparoscopy or laparotomy for intra-abdominal testicles add up. Costs range from 300 to 1,000+ euros, depending on the clinic and the location of the testicles. Consult a veterinarian or specialist for preoperative planning.

Related terms

• Neutering in Dogs
• Testicular Tumor in Dogs
• Reproduction in Dogs
• Dog Breeding
• Developmental Disorders in Dogs

Sources & Further Reading

1. Yates, D., Hayes, G., Heffernan, M., & Beynon, R. (2011). Incidence of cryptorchidism in dogs and cats. Veterinary Record, 168(16), 408. 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. Journal of Veterinary Medical Science, 71(7), 919–923. https://pubmed.ncbi.nlm.nih.gov/19743399/

3. Hayes, H. M. (1986). Epidemiological features of 5009 cases of canine cryptorchidism. Journal of Small Animal Practice, 27(1), 1–14. https://pubmed.ncbi.nlm.nih.gov/3701507/