At birth, the testicles of a puppy are still within his abdomen. As the animal develops, the testicles slowly 'descend' into the scrotum. In mammals, sperm development does not occur correctly at the high temperatures found within the body. The testicles are therefore held outside of the abdomen and within the scrotum to provide a cooler environment. The production of testosterone is usually not influenced by temperature.

Frequently, owners notice that the puppy they just purchased only has one or possibly no testicles within the scrotum. Although different dates are listed in some of the veterinary literature, both testicles are usually within the scrotum by the time the animal is six weeks of age and they should definitely be there by the time the puppy is eight to ten weeks of age. If one or both testicles are not present at that location by twelve weeks of age, they probably never will be and the animal is said to be suffering from cryptorchidism or 'retained testicles.' This is a disorder that may be passed from generation to generation.

What are the symptoms?

These animals rarely show any abnormalities because of this condition. They have normal activity levels, growth, and behavior. Although fertility may be affected, they will usually show normal breeding behavior and frequently impregnate females, especially when one of the testicles has descended into the scrotum.

What are the risks?

Some researchers believe that dogs with cryptorchidism may have a higher incidence of other testicular diseases. Specifically, these would be cancer and torsion.

What is the management?

Cryptorchid dogs should never be allowed to breed. This is a well-documented genetic trait, passed on to future generations. In addition, because of the potential for an increased incidence of torsion or cancer within the retained testicle, it is strongly recommended that all of these individuals be neutered. The surgery to remove a retained testicle is more involved than a routine neuter. The veterinarian must literally hunt for the testicle, which may be located anywhere from the area around the kidney in the abdomen to the muscle near the groin.

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Cryptorchidism = lack of descent of one or both testicles into the scrotum by 6 months of age. The retained testicle(s) may be found at the inguinal ring, in the inguinal canal, or in the abdomen.

Normal testicular descent - The testes develop initially caudal to the kidneys, attached to the superficial inguinal ring by the gubernaculum testis. The gubernaculum grows, pulling the testicle through the abdomen and inguinal canal, and then shrinks, pulling the testicle into the scrotum. The process is dependent on physical presence of the testis. Testosterone is important only late in descent. Factors controlling gubernacular outgrowth are unknown.

Cryptorchidism is due to hormonal, genetic and/or physical-environmental factors altering gubernacular outgrowth and movement of the testis. In rats, cryptorchidism is associated wtih decreased androgen secretion, decreased smooth muscle content in the gubernaculum or decreased sympathetic tone in the gubernaculum. Canine cryptorchidism is believed to be a sex-limited hereditary trait with transmission due to a single autosomal recessive gene. The genetic predisposition may be carried by males or females, although it will only be manifested in males.

Incidence - This is a common disorder with purebred dogs more susceptible than crossbreds (perhaps due to inbreeding), with toy breeds predisposed, and unilateral cryptorchidism more common than bilateral with the right side more commonly retained.

The risk of testicular neoplasia and torsion is increased in retained testicles.

The unilateral cryptorchid is fertile. Retained testicles are incapable of spermatogenesis due to elevated abdominal temperature destroying spermatogenic tissues, but are capable of steroidogenesis.

Breeding of unilateral cryptorchids should be discouraged. Neuter them! This condition is hereditary, and the dog is at increased risk of testicular torsion and neoplasia. Cryptorchid dogs cannot be shown in sanctioned dog shows.

  • Puberty, defined as presence of spermatozoa in the ejaculate and normal breeding behaviours, occurs from 6 to 24 months of age, with an average of 10 to 12 months of age.

  • Anatomy:
    The two testicles should be completely descended by 6 months of age. The two testicles should be completely descended by 6 months of age. Testicular size varies with size of the dog. and can be evaluated by measurement of total scrotal width (Woodall PG, Johnstone IP. J Sm Anim Prac 1988;29:543). The prostate is the only accessory sex gland. The penis of canids contains a bone, the os penis.

(kg) [lbs]



5 [11]



10 [22]



15 [33]



20 [44]



25 [55]



30 [66]



35 [77]



40 [88]



45 [99]



50 [110]



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