Cryptorchidism only affects a small percent of male cats. When the kitten is two to four months of age, a diagnosis can generally be made, although some veterinarians prefer to wait up to 9 months to treat the condition. The testicles can be retained in various parts of the groin area, including inside the abdomen, the inguinal region (where the abdomen and rear legs connect) and just beneath the skin in the groin tissue. Veterinary treatment is necessary to eliminate serious conditions that can develop later in the cat’s life.

At birth,a kitten’s testicles are located inside the abdomen near the kidneys. Over the next few months, the testes descend down to the groin and out into the scrotal sac. Rarely, one or both of the testes fails to descend all of the way to the scrotum. This condition is referred to as cryptorchidism. If only one testis fails to descend, it is termed unilateral, whereas if  both testes are affected it is called bilateral. Bilateral cryptorchidism is far less common than unilateral. 

The cat will generally not exhibit any concerning health symptoms unless the retained testicles are left in the body until adulthood. While serious complications are rare, they can develop. Symptoms to watch for include:

While the exact reason that some cats fail to have their testicles descend is unknown, the condition does seem to affect purebred cats exponentially more than mixed-breed house cats. Depending on the breed, instances of cryptorchidism may be as high as 30%. Breeds commonly affected include Persians and Himalayans. This genetic predisposition may be exacerbated by inbreeding and continuing to breed affected males.

Undescended testicles are often discovered at a kitten’s first vet visit and physical examination. Often, testicular palpation can confirm the absence of testes in the scrotum. In some cases, the testes may be felt elsewhere in the groin under the skin. If only one or none can be found, generally this means that the testes are deep in the abdomen. X-rays or ultrasound imaging will be needed to locate and assess the retained testis. If only one testicle has been affected, it will appear much smaller than the functional testicle. 

Blood work may be required, including a testosterone level test and a complete blood count to see if there is any malignancy in the body. If the cat has been rescued and you are unsure if it has been castrated or if it's testicles are retained within the body, the penis will be checked for the presence of barbs. If barbs exist and the cat is over nine months, cryptorchidism can be confirmed. If a testis is proving difficult to find, following the ductus deferens on an X-ray image can help locate the retained testis. 

Once cryptorchidism has been diagnosed, treatment should be sought as soon as possible. Some veterinarians will not operate before the cat is nine months old, however there is little research to confirm this is of any benefit to the cat. There is no procedure to bring the testis down into the scrotum.

Even if only one testicle has failed to descend, both should be surgically removed. This will prevent further complications and will ensure that the cat will not pass on this genetic defect to any kittens. The neutering process on cats with cryptorchidism is slightly more complicated than a regular castration. Two separate incisions will need to be made if one testicle is retained in the abdomen or within the inguinal canal. If both testicles are retained in the abdomen, one incision is needed but the surgery is slightly more invasive. Occasionally, a testicle may become trapped in muscular tissue. Maneuvering the area with a blunt instrument can push the testis back up into the abdomen where it can then be removed. 

After your cat has undergone surgery, it is important to follow all at-home care instructions from the veterinarian. Activity should limited through the duration of healing and the cat should be kept indoors. An Elizabethan collar may be necessary to keep your cat from licking or biting at his incision. Monitor the incision site for redness, swelling or any other possible signs of infection. If the testicles were located in the abdomen, the recovery period will be longer than a normal neuter. Prognosis for cats who have undergone this surgery is very good, with most cats leading long and normal lives.

There is no way to prevent instances of cryptorchidism. Selective breeding should be used to help decrease cases of cryptorchidism. Cats who have produced kittens with genetic defects, or who possess genetic defects themselves, should not be allowed to reproduce. Performing a full neuter on affected cats will help reduce the chance of cancer development and will prevent the possibility of testicular torsion. It will also eliminate unwanted male cat behaviors.