In normal male canines, the testicles develop in the abdomen and then descend into the scrotum before or shortly after birth. In pups with a condition known as cryptorchidism, however, either one or both testicles fail to descend within two months after birth and are left underdeveloped and non-functional. The undescended testicle(s) may remain inside the abdominal cavity or else drop into the groin tissues outside of the scrotum.
Cryptorchidism normally goes unnoticed by the dog's owner, and is typically diagnosed in young, healthy dogs when they are taken to the veterinarian to be neutered. Diagnosis is a simple procedure -- the veterinarian will palpate the scrotum, and if one or both testicles are absent, the condition is confirmed. On rare occasions, someone may adopt a dog that they believe has already been castrated, only to find out that the animal actually has cryptorchidism. In these cases, your veterinarian may perform abdominal ultrasound exams and/or measure the dog's blood testosterone levels to confirm the diagnosis.
The physiology behind the condition is somewhat complex. In dogs a tube called the vaginal process runs along the inner lining of the abdomen to the scrotum, enclosing the latter. The tube contains the male reproductive organs, including the spermatic cord and vas deferens, as well as arteries, veins, nerves and the cremaster muscle.
This muscle is designed to pull the testicles closer to the body in cold environments and allow the scrotum to hang lower when the atmosphere is warm. In the normal abdominal wall there also is a ring-shaped passageway that the testicles move through as they drop shortly after birth. In cases of cryptorchidism, either one or both testicles stay inside this wall, and the opening shrinks after birth, trapping the testicles within the abdominal cavity.
Two possible theories exist regarding the cause of this condition. The first is that there is a genetic defect in the length of the spermatic cord that does not allow the testicles to descend. Some cases also may be caused by a defect in the cremaster muscle. Many veterinarians believe that problems with this muscle cause a related condition known as "elevator testicle," in which testicles bounce up and down between the scrotum and the abdominal cavity. In many dogs, this condition exists at birth but is outgrown before the animal is a year old.
Cryptorchidism is believed to be hereditary and may be passed on if an affected animal is bred. Any breed can be affected. Removal of both testicles in these dogs is recommended, since these animals have been found to be at a higher risk for testicular cancer. The procedure normally is performed by making an incision in the skin of the groin or abdomen and surgically removing the testes. Most animals recover promptly from the surgery, but will need to be kept quiet and indoors for about two weeks post-op. The incision also should be kept clean and dry. Some animals require a cone-shaped "collar" around their neck in order to keep them from licking or chewing at the incision while it heals.
Dog with cryptorchidism normally lead healthy, full lives following surgery, although they usually will no longer qualify as show animals.