Cryptorchidism is a condition in which a male’s testicles have not descended (dropped) into the scrotum as they mature. At birth, a male puppy’s or kitten’s testicles are located in the abdomen close to the groin in an area called the inguinal ring. By 2 to 3 weeks of age, typically, they’re in the puppy’s scrotum. By 6 months of age, they’re palpable in the kitten’s scrotum.

The arrow shows a retained testicle in the
inguinal canal. The scrotum has a single testicle

In the fetus, a structure called the gubernaculum connects the testicle (located next to the kidney during development) to the scrotum. If this structure fails to develop properly, the testicle will not end up in the scrotum, but will end up in the abdomen, the inguinal canal, etc.

Cryptorchidism can affect only one testicle (unilateral)or occur to both testicles (bilateral). Unilateral cryptorchidism usually involves the right testicle. Animals that have bilateral cryptorchidism are usually sterile because the higher body temperature inside the abdomen is enough to prevent sperm production. The animals will, however, still exhibit male behaviors as sex hormones like testosterone are still produced.

Normal dog with 2 testicles in scrotum

Cryptorchidism is a fairly common defect in dogs. Dog breeds most likely to be affected include Yorkshire terrier, Pomeranian, French poodle, Siberian husky, miniature schnauzer, Shetland sheepdog, Chihuahua, German shepherd, dachshund, and brachycephalic breeds, but it can happen in any breed or mixed breed. It’s considered to be a recessive trait and can be passed on to offspring. For this reason, if an animal is cryptorchid, he should not be used for breeding. 

Other problems that affect cryptorchid animals are: testicular torsion and testicular cancer, so these individuals should be neutered to prevent problems later.

Cryptorchidism in cats is uncommon. The most common breed associated with cryptorchidism is the Persian. Congenital abnormalities that have been known to occur simultaneously with cryptorchidism are: patellar luxation, shortened tail, kinked tail, a developmental heart defect called tetralogy of Fallot, hind limb deformities, abnormally small eyeballs, and upper eyelid developmental issues. Unlike dogs, it may be possible to visually differentiate between a castrated cat and one with retained testicles, because cryptorchid cats have barbs on the penis.

Laboratory Diagnosis

If an animal is found that does not have visible testicles but is displaying male behavior, a testosterone assay can be used to determine whether the animal is neutered or has two retained testicles.

Treatment

RETAINED TESTICLES IN DOGS

Surgical removal is the only treatment for cryptorchidism. Even if the animal is a unilateral cryptorchid, both testicles should still be surgically removed. (The cryptorchid testicle should be removed to prevent testicular torsion and testicular cancer, and the normal testicle should be removed to prevent cryptorchid offspring). 

This surgery is more complicated than the usual neuter surgery, because the cryptorchid testicle can be difficult to locate. Depending on the case, some pets will be able to go home the day of the surgery, and some may have to stay in the hospital overnight. A 2-week recuperation (reduced activity) is advised because this surgery usually involves opening the abdomen, and the surgical site has to have time to heal before the pet resumes normal activities.

Prognosis

Cryptorchid animals that have had both testicles removed, and have no other defects, will generally live a normal lifespan for the breed.

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