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In:  Recent Advances in Small Animal Reproduction, Concannon P.W., England G., Verstegen III J. and Linde-Forsberg C. (Eds.)
International Veterinary Information Service, Ithaca NY (, 2001; A1224.0701

Canine and Feline Cryptorchidism  (Last Updated: 1-Jul-2001)

M. Memon and A. Tibary
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, USA.
Cryptorchidism in Dogs and Cats
There should be two normal testes present in the scrotum of a male to be used for breeding (Fig. 1). A non-castrated male with no testes present in the scrotum is a bilateral cryptorchid (i.e., a bilaterally cryptorchid individual). A male with only one testis present in the scrotum (Fig. 2) is a unilateral cryptorchid. The term cryptorchid means hidden testicle. Unilateral cryptorchidism occurs more commonly than the bilateral condition.
Figure 1. Normal anatomy of the scrotum and testicles in the dog. Testicular descent should be completed by 6 months of age. The testicles should be readily palpable within the scrotum.

Figure 2. Unilateral cryptorchidism in a 9-month old dog. 

The owners of such animals often inquire "how long should I wait before giving up that the undesecended testis is going to come down?" Testicular descent is complete by about day 10 after birth in normal dogs. Some owners of cryptorchid animals may report presence and disappearance of scrotal testes. In a newborn puppy or kitten, the testes are small, soft and can move between scrotum and inguinal canal, especially when the pup is stressed or frightened. It is recommended to wait up to about six months of age before declaring a dog or a cat cryptorchid. The reason for the six-month wait is that the inguinal rings of most dogs are closed by 6 months of age, precluding movement of the testes from the abdomen to the inguinal canal if that has not already occurred.
Cryptorchidism is heritable and is a sex-limited autosomal recessive trait in dogs. The incidence of cryptorchidism seems to be higher in purebred and inbred dogs than in mixed-breed dogs. High prevalence of cryptorchidism within lines of inbred Cocker Spaniels and miniature Schnauzers has been reported. High frequency of other congenital defects noticed in cryptorchid dogs include inguinal and umbilical hernias, patellar luxation, and preputial and penile problems. Retained testes also have a tendency to develop neoplasic changes. The risk of neoplasia in retained testis has been reported to be 9 to 14 times higher than in the scrotal testis, with Sertoli cell tumors and seminomas being the most common tumors.
In cats, however, there is no information available to show cryptorchidism as a hereditary condition. Some clinicians consider it hereditary condition because of its hereditary nature in other domestic animals.
A unilaterally cryptorchid animal can produce sperm, whereas a bilateral cryptorchid male usually does not produce sperm and is sterile. Testes should be scrotal and thus 4 to 5 degrees cooler than the body temperature to produce normal sperm. Even though unilateral cryptorchids produce abnormal sperm quality, due to adverse effect of high body temperature in the abdominal cavity, they can impregnate a female in estrus. Cryptorchidism however, does not affect testosterone production. Therefore, most of the cryptorchids show sexual desire and can achieve erection. Retained testes are smaller and, viewed histologically, the diameter of the seminiferous tubules is reduced by up to 60 % compared to those of scrotal testes. A higher incidence of cryptorchidism has been reported in small-breed compared to large-breed dogs. Reported incidences in dogs range from 1.2 to 10 %. The top ten breeds with increased incidence of cryptorchidism are Toy Poodles, Pomeranian, Yorkshire terrier, Miniature Dachshund, Cairn terrier, Chihuahua, Maltese, Boxer, Pekingese, and English bulldog.
Visual examination and careful digital palpation of the scrotum and inguinal area is helpful. However, scrotal fat and inguinal lymph nodes may be confused with the retained testis. Abdominal testes are difficult to palpate or visualized by ultrasonography (US). The use of human Chorionic Gonadotrophin (hCG) or Gonadotropin Releasing Hormone (GnRH) Stimulation Test for inducing a measurable testosterone increase is recommended. Commercial bovine GnRH products, Cystorelin ® or Factrel ® may be used. The standard protocol for this test is to determine testosterone levels in a blood sample drawn before and 60 minutes after injection of GnRH at doses of 2 mg/kg or 50 mg/dog, IM. An increase in testosterone concentrations in the post-treatment blood sample would, in such cases, be diagnostic for a cryptorchid dog.

Castration or removal of both testes is the treatment of choice for cryptorchidism. As discussed above, in dogs, crytorchidism is considered hereditary and a dog with this condition should not be used for breeding. There is an increased incidence of Sertoli cell tumors in abdominal testes. Although not a common occurrence, torsion of the spermatic cord may occur with an abdominal testis, and may lead to sudden abdominal pain and other complications. The surgical approach for finding and removal of the cryptorchid testis is dependent on the location of the testis. The key for finding the retained testis is to identify and follow the ductus deferens leading to the testis. The retained testis may be removed by laparoscopy.
Orchiopexy or surgical placement of the retained testis into the scrotum is not recommended, although it can be done successfully. Kawakami, et al., have reported pregnancy results in bitches bred with dogs following orchiopexy. Gradual improvement in semen quality was noticed and 3 out of 11 bitches bred were diagnosed pregnant. However, cryptorchid dogs cannot be shown in American Kennel Club shows and treatment by orchiopexy may be considered fraudulent.
The most common medical treatment, not including acupuncture and herbal medicine, is the use of drugs providing luteotrophic hormone (LH) activity, such as hCG or GnRH to induce an increase in endogenous LH]. Most of the studies reporting the success of the hormonal treatment are based on clinical case follow-ups and lack control cases. Control of cryptorchidism can be accomplished by removal of the cryptorchid dogs and preferably their dam and sires from breeding programs.


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Mount Airy, NC 27030
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