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Basics ⬇

Basics

Overview

  • The incomplete descent of one or both testes into the scrotum is the most common congenital anomaly of the testes.
  • Inguinal-retained testis often palpable.
  • Abdominal-testis difficult to palpate or identify by radiology; ultrasonography is the best available option to determine size and location of testis.
  • Descent to final scrotal position-expected to be complete by 2 months postpartum; may occur later in some breeds, but rarely after 6 months in any individual; presume the diagnosis if no palpable testes at 2 months.
  • Beagles-testes at the exterior inguinal ring by day 5 postpartum, between the inguinal ring and scrotum by day 15, and in the scrotum by day 40.

Signalment

  • Dog-reported in almost all breeds; Chihuahua, toy poodle, Pomeranian, Yorkshire terrier; toy and miniature breeds are 2.7 times at greater risk to be cryptorchid than larger breeds; in certain populations German shepherd dog, boxer, and Staffordshire bull terrier also have greatly increased risk; unilateral more common than bilateral (75:25); right testis retained twice as often as left in dogs; right and left testis retained at equal frequency in cats.
  • Incidence-dogs, ranges of 0.8–10% have been reported, incidence increases with the proportion of purebred dogs in the population; cats, 1–1.7%; 50% incidence in miniature schnauzer affected with persistent Müllerian duct syndrome.
  • Genetics (dogs)-exact mode of inheritance unknown; complex genetic basis; likely polygenic recessive trait; likely heritable.
  • Genetics (cats)-may be inherited, but no data documents hereditary defect; Persians overrepresented in surveys.

Signs

  • Bilaterally cryptorchid animals are infertile; unilaterally cryptorchid animals are typically fertile.
  • Rarely associated with pain or other signs of disease.
  • Acute onset of abdominal pain-spermatic cord of retained testes at increased risk for torsion; 36% of retained testes with torsion of the spermatic cord were neoplastic.
  • Feminizing paraneoplastic syndrome-estrogen-secreting Sertoli cell tumors in retained testes produce feminizing signs: gynecomastia, symmetrical alopecia of trunk and flanks, hyperpigmentation of inguinal skin, pendulous preputial sheath, prostatic squamous metaplasia.

Causes & Risk Factors

  • Removal of affected males from breeding lines-believed to cause a reduction in frequency; heritability thought to involve more than one gene.
  • Non-hereditary predisposing factors (e.g., birth weight)-identified in humans; not reported in dogs.

Diagnosis ⬆ ⬇

Diagnosis

Differential Diagnosis

  • Castration-differentiate bilateral condition from previous castration, previous castration of single scrotal testis with retained abdominal testis, or anorchidism (rare).
  • Bilaterally cryptorchid cats may have urine odor and behavior of intact cats.

Other Laboratory Tests

hCG stimulation test-doubles blood testosterone with bilateral condition; doubles blood testosterone with unilateral condition in which only the scrotal testis has been removed; differentiates between cryptorchidism and castration; administration of 750 IU hCG IV or 50 µg GnRH IM with blood sample collection pre- and 2–3 hours post-injection; castrated dogs have testosterone concentrations <0.1 ng/mL and do not stimulate with hCG or GnRH administration. Determination of blood canine anti-Müllerian hormone (produced by Sertoli cells; Spaycheck®) has also become commercially available for the diagnosis of cryptorchidism (uni- or bilateral conditions).

Imaging

Transabdominal ultrasonography-useful to locate testes in the inguinal or abdominal regions. Recommended before laparotomy or laparoscopy to remove cryptorchid testes.

Treatment ⬆ ⬇

Treatment

Medications ⬆ ⬇

Medications

Drug(s)

  • hCG (dogs)-100–1,000 IU IM four times in a 2-week period before 16 weeks of age (dogs); after 16 weeks, generally unsuccessful.
  • GnRH (dogs)-50–750 µg one to six times between 2 and 4 months of age.

Follow-Up ⬆ ⬇

Follow-Up

Miscellaneous ⬆

Miscellaneous

Associated Conditions

  • Inguinal hernia, umbilical hernia
  • Hip dysplasia
  • Patellar luxation
  • Penile and preputial defects (e.g., hypospadias)

Abbreviations

  • GnRH = gonadotropin-releasing hormone
  • hCG = human chorionic gonadotropin

Author Carlos R.F. Pinto

Consulting Editor Sara K. Lyle

Suggested Reading

Birchard SJ, Nappier M. Cryptorchidism. Compend Contin Educ Pract Vet 2008, 30(6):325–337.

England GCW, Allen WE, Porter DJ. Evaluation of the testosterone response to hCG and the identification of a presumed anorchid dog. J Small Anim Pract 1989, 30(8):441–443.

Feldman EC, Nelson RW. Canine and Feline Endocrinology and Reproduction. Philadelphia: Saunders , 1987, pp. 697–699.

Felumlee AE, Reichle JK, Hecht S, Penninck D, Zekas L, Dietze Yeager A, Goggin JM, Lowry J. Use of ultrasound to locate retained testes in dogs and cats. Vet Radiol Ultrasound 2012, 53(5):581–585.

Johnston SD, Root Kustritz MV, Olson PNS. Disorders of the canine testes and epididymes. In: Canine and Feline Theriogenology. Philadelphia: Saunders, 2001, pp. 312–332.

Memon M, Tibary A. Canine and feline cryptorchidism. In: Concannon PW, England G, Verstegen III J, Linde-Forsberg C, eds., Recent Advances in Small Animal Reproduction. International Veterinary Information Service, Ithaca NY, www.ivis.org, 2001; A1217.0901.