Health & Diseases

Undescended Testicle in Dogs (Cryptorchidism): Causes & Treatment

Cryptorchidism refers to the failure of normal testicular descent — one or both testicles do not fully descend into the scrotum but remain in the abdomen, inguinal canal, or subcutaneously in front of the scrotum. The testicle should have fully descended by 8 weeks of age; a male dog with two non-palpable testicles in the scrotum at 6–8 weeks of age is suspected of having cryptorchidism.

Undescended testicle in dogs (cryptorchidism): causes & treatment

What is an undescended testicle in dogs?

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

Cryptorchidism is one of the most common congenital anomalies in dogs — unilateral (more common, with the right side more often affected) or bilateral. It has a genetic component and should be taken into account in breeding.

Background + scientific context

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

Liao et al. (2009, JAVMA, PubMed 19743399) analyzed 232 dogs with testicular tumors in cryptorchid testes: the tumor risk in the retained testicle is 9–13 times higher than in a normally descended testicle. Sertoli cell tumors predominate in retained testes and can cause feminization syndrome (due to estrogen production). Early surgical removal of the retained 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 epidemiological studies: right-sided undescended testicle was more common than left-sided; unilateral cryptorchidism was more common than bilateral. No spontaneous resolution after 6 months of age was to be expected. This study was the first to comprehensively demonstrate the association between a retained testicle and an increased tumor risk.

Vitomalia position

A retained testicle is not a cosmetic issue — it is a proven tumor risk. Cryptorchid dogs should be castrated before the risk becomes manifest. From a breeding perspective: cryptorchidism has a genetic component, and affected dogs and their close relatives should not be used for breeding.

When does cryptorchidism become relevant in dogs?

  • In male puppies: testicles palpable by 8 weeks? control until 6 months
  • In affected dogs: castration recommended (tumor risk, hormonal complications)
  • With signs of feminization syndrome: coat changes, pendulous prepuce, gynecomastia (indication of Sertoli cell tumor)
  • In breeding: exclude cryptorchid dogs, genetic counseling
  • If testicular status is unclear before castration: abdominal testicle localization is necessary

Practical application

Localization of the retained testicle:

Position Frequency Diagnostics
Inguinal canal/subcutaneous ~75% Palpation
Intra-abdominal ~25% Ultrasound, exploratory laparotomy
Bilateral ~25% of all cryptorchidism cases Clarify both locations

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

Feminization syndrome with Sertoli cell tumor: symmetrical alopecia, feminization, bone marrow suppression — castration in the short term.

Common mistakes & myths

  • “The testicle will still come down on its own.” After 6 months of age, spontaneous descent is no longer expected. Waiting extends the tumor-risk window.
  • “One testicle is enough for castration — we’ll leave the other one.” No: the retained testicle has a 9-fold increased tumor risk. Both testicles must be removed.
  • “Cryptorchidism is not a breeding taboo.” A genetic component is established — cryptorchid dogs and affected sires/sons should be excluded from breeding programs.

Scientific status 2026

Genetic studies are increasingly identifying candidate genes for cryptorchidism in dogs (including on the Y chromosome). In specialized clinics, laparoscopic testicle removal has largely replaced open surgery for abdominal testicles. 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 castrated?

Recommendation: from 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 tumor risk. Early castration prevents testicular tumors, torsion of the retained testicle, and hormonal complications.

Can a cryptorchid dog be fertile?

Unilaterally cryptorchid dogs can produce fertile sperm through the normal testicle — but they should not be used for breeding (genetic transmission). Bilaterally cryptorchid dogs are usually infertile because both testicles are too warm for spermatogenesis.

What does castration for cryptorchidism cost?

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

Related terms

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/

Wissenschaftliche Einordnung

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 breed differences. Small breeds (Yorkshire Terriers, Chihuahuas, Pomeranians, Maltese) had a significantly higher prevalence than large breeds. A genetic predisposition is 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 tumor risk in the retained testicle is 9–13 times higher than in a normally descended testicle. Sertoli cell tumors dominate in retained testicles and can cause feminization syndrome (due to estrogen production). Early surgical removal of the retained 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 epidemiological studies: Right-sided cryptorchidism was more common than left-sided; unilateral cryptorchidism was more common than bilateral. No spontaneous resolution was expected after 6 months of age. The link between retained testicles and increased tumor risk was comprehensively demonstrated for the first time in this study.