This very common, heritable condition of male dogs and cats manifests as a congenital abnormality in the position of one or both testicles. Affected animals are otherwise normal.
Embryologically, the testicles originate near the rudimentary kidney and are destined to migrate so that they'll reside within the pubis-positioned scrotum. When one or both testicles do not reach their intended destination the resulting condition is called "undescended testicle(s)" or cryptorchidism. The undescended testicle(s) may reside either in the abdomen or under the skin near the scrotum.
While it would seem that cryptorchidism is a fairly benign condition, a trio of problems can be related to its occurrence:
affected animals are sterile in the undescended testicle(s), as the affected gonad will typically fail to develop normally outside its normal position in the scrotum
animals with only one undescended testicle (a reported 75% of cryptorchid cases) are potentially able to pass on the hereditary trait associated with cryptorchidism, and
in their abnormal position, the undescended testicle(s) are more susceptible to cancers and torsion (a twisting that may lead to a reduced blood supply and tissue death).
In dogs, cryptorchidism is believed to be a sex-limited autosomal recessive trait, though the mode of inheritance may differ from breed to breed.
Symptoms and Identification
An estimated 13% of all dogs are affected at least unilaterally. The incidence is significantly lower in cats but the condition is considered relatively common nonetheless. Animals are easily identified via palpation of the scrotum.
The following breeds seem to be the most predisposed:
Treatment is undertaken via sterilization.
Because cryptorchidism requires sterilization and because cryptorchid sterilization is not considered routine, the expense associated with treating cryptorchid animals is necessarily higher than for non-affected animals. Intra-abdominal surgery (laparotomy) is required unless the testicle is positioned just beneath the skin). For this reason, "cryptorchid neuter" surgeries are often priced similarly to the intra-abdominal surgery undertaken for female sterilization (spay).
Removing affected animals and their parents from the breeding pool is considered a basic tenet of cryptorchidism prevention. Because estrogen exposure during pregnancy has also been associated with cryptorchidism, care should be taken to minimize a bitch or queen's exposure to exogenous hormones during gestation.
Merck Veterinary Manual
The Veterinary Record, Vol 152, Issue 16, 502-504 Copyright (c) 2003 by British Veterinary Association
Incidence of cryptorchidism in dogs and cats D. Yates BVSc1, G. Hayes MA1, M. Heffernan MVB1, and R. Beynon BVSc1