Primates in which both testicles fail to descend are sterile. When testicles remain in the abdomen the 4-5 degree higher temperature there prevents the production of sperm. It does not, however, affect the production of testosterone, so these pets exhibit typical male behavior. When one testicle does descend into the scrotum the pet will be fertile. It is a bad idea to breed because their descendants may show or carry the same defect.

Sertoli Cell Tumors:
Cryptorchid Primates have a higher rate of developing a certain cancer call a Sertoli cell tumor. The Sertoli cells, which are located in the testicles, provide nourishment to the sperm cells. They also produce feminizing hormones (estrogens). These tumors often cause thin skin, sparse hair coat, aplastic anemia, enlarged breasts and attractiveness to other male dogs. The hair loss in these cases is very specific in that it is identical on both sides of the trunk (bilaterally symmetrical). We diagnose this tumor by this distinctive pattern of hair loss that occurs in a cryptorchid dog or cat. Occasionally we may need to do ultrasound examination of the retained testicle as well as a plasma estrogen level to confirm the diagnosis. Ten to twenty percent of these tumors are malignant and can metastasize (move) to other parts of the body.. If the tumor has spread it can be treated successfully with chemotherapy consisting of vinblastine, cyclophosphamide, and methotrexate. To avoid this debilitating treatment, we veterinarians suggest that the cryptorchid testicle be located and removed before it has the opportunity to becoming cancerous. Another problem that occurs in rare instances in cryptorchid pets is torsion of the spermatic cord , the sperm duct attached to the testicle.

Diagnosis And Therapy:
Cryptorchidism in Capuchins over twelve weeks of age is self-evident on physical examination. One only needs to pass the scrotum through pinched fingers to notice that only one or none of the testicles are present. In more than half of the cases I can palpate the missing testicle in the fat located in the animals groin. In these case I have read that the testicle can be relocated into the scrotum. I have also read that testosterone therapy sometimes allows the retained testicle to descend into the scrotum. I have performed either of these procedures because I do not wish to play a part in perpetuating the disease to future generations of Primates. Instead, I remove the retained testicle along with the normal one when I neuter the pet.

A special problem comes up when an adult Primate that appears to be castrated still exhibits male behavior. Here, we can be uncertain if we are dealing with a castrated Primate or a cryptorchid Primate. Sometimes the retained testicle can be visualized in the abdomen with ultrasound. When this is not the case, the pet can be given an injection of bovine (cow) chorionic gonadotropin. If this hormone causes a rise in serum testosterone level one hour after injection we are dealing with a cryptorchid pet. When this question occurs in a cat, we can examine the penis for spines. Spines are much smaller in castrated cats than in cats that still have their testicles – cryptorchid or not.

When the missing testicle or testicles have not passed through the inguinal ring and are still located in the abdomen, the surgery is much more complicated. In effect, you must neuter and spay the same animal. The missing testicle can be anywhere between the posterior pole of the kidney and the inguinal ring and it can be nerve racking to find and remove it. These testicles are much smaller and softer than the descended ones and are extremely difficult to locate in the fat that occupies the posterior abdominal space. What usually allows me to find them is the epididymus or sperm collecting tubules that retain their distinctive appearance.

Primates that are cryptorchid have a higher incidence of other genetic defects such as inguinal and umbilical hernias, abnormally formed penis and sheath, as well as patellar luxations (trick knees).

Some authorities suggest waiting up to six months before deciding that the testicle(s) are not going to descend. I have never seen a case where the testicle(s) were not descended at twelve weeks of age but descended later. Surgery is always easier on a pet when it is young so don’t put off the surgery too long.