Cryptorchidism is a health problem in male dogs where two testes develop, but only one of them drops down into the scrotum from within the body. This process should naturally occur by the time the puppy is between two and six months old, depending on its breed. Retaining one testis is known as unilateral cryptorchidism, while retaining both is called bilateral cryptorchidism. Another form of this problem exists, called monorchidism, however. Unlike cryptorchidism, monorchidism occurs when only one testis develops to descend into the scrotum. Cryptorchidism and monorchidism are often confused, so it will require a veterinarian to remedy either condition.
What causes the retention of the testes, or the production of only one testis, has yet to be determined other than being a genetic flaw. Some scientists claim it may happen during fetal growth due to the twisting up and loss of blood to the testis. It has been noted as occurring more often in purebred dogs and is inheritable through the male's genes. In monorchidism, the testis is not undescended through the inguinal canal or higher in the abdomen; only one testis drops because only one has developed.
No real pain or discomfort usually surrounds monorchidism. Dogs are not ill when they have this problem as no undescended testis occurs within the body to tangle or otherwise cause significant damage. There will only be one testicle that descends.
Monorchidism is a rare developmental condition. The diagnosis comes in a variety of ways: palpation of the scrotum and inguinal canal to check for other testicular tissues; ultrasound to determine if any other tissues may exist deeper inside the abdomen, away from palpation and X-ray analysis; and plasma testosterone analysis. Plasma testosterone analysis is done to check the levels of plasma testosterone, as it will be significantly lower in a dog with only one developed testis.
Monorchidism may not be a significant source of discomfort for a dog, unless there are additional complications, according to the Pet MD website. Bari Spielman, DVM, asserts that neutering is the most common treatment for monorchidism. Breeding animals will pass this abnormality on to their offspring genetically, especially if inbreeding and line-breeding is done.
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