If your dog does not have two visible testicles by the second month after birth, you need to have your veterinarian check for cryptorchidism, or retained testes. While many owners think having retained testes is not a big deal and just ignore it, this can put your dog at a much higher risk of getting testicular torsion or cancer. Both of these illnesses are extremely painful and can be fatal. Cancer of the testicles is the second most often reported cancer in dogs overall and about 12 times more common in dogs with retained testes. This cancer can lead to symptoms including abdominal swelling and weight loss. Testicular torsion is usually rare, but with the testes floating around unattached in the abdomen it is much more common and a life-threatening emergency. It occurs when the testicle twists itself up and cuts off the circulation to that testicle. Extreme pain and infection are imminent and emergency surgery to remove the testicle will have to be done immediately to save your dog.

Retained testes happen when the tube that connects the testicle to the scrotum does not form correctly, the testicle will not be able to drop down into the scrotal area as it should. It is actually fairly common in dogs, although unilateral cryptorchidism is the most common. There are two types; unilateral, which means only one testicle has descended, and bilateral, which means neither testicle drops into place in the scrotum. In unilateral cryptorchidism it is the left testicle that descends in most cases. Those with bilateral cryptorchidism are almost always sterile because it is too hot inside the abdomen for sperm to live.

When one or both of a dog’s testes do not drop down into the scrotal area, this is called cryptorchidism, which is also called undescended or retained testes. There are two types of retained testes, which are unilateral (only one testicle drops down) or bilateral (both testes do not drop down). By the eighth week of a dog’s life their testicles should have both fallen into place in the scrotal area behind the kidneys. If one or both testicles do not drop into the scrotum, this can cause more than just cosmetic issues. It can also affect the health of the dog by increasing the risk of cancer or testicular torsion. A dog with retained testes will almost always be sterile, but it is still essential to get your dog neutered to prevent cancer or torsion.

The most obvious sign that your dog has retained testes is if your dog has only one testicle or none at all. Even if you do not notice this, your veterinarian will catch the problem at your puppy’s first examination. That is why it is so important to take your puppy to the veterinarian between six and eight weeks of age for the first check-up.  Sometimes, a puppy's testicle may drop down at a later age (e.g. 3 or 4 months).

Signs of a problem down the line can include:

While this is not uncommon in any dog, it is more common in certain breeds, which are:

Although this condition should be noticed by the veterinarian at your puppy’s first examination between six and eight weeks, sometimes it may go unnoticed until a later age. A good example of this is if you get your dog when it is older and the first owner did not get the puppy checked by a veterinarian or if your male dog was mistaken for a female because it has bilateral cryptorchidism (although this would be rare as their penis should still be visible). Either way, provide the veterinarian with as much information about your dog’s history as you have. This should include medical records, vaccinations, illnesses or injuries, changes in behavior or appetite, and any symptoms you have noticed.

Your veterinarian will then do a physical examination of your dog. A complete physical exam will include heart rate, weight, body temperature, and blood pressure. After the examination, the veterinarian may do some tests, including urinalysis, stool sample, semen sample, x-rays, and ultrasound. He may also need to do a CT scan and/or MRI if necessary to see exactly where your dog’s testicle(s) are located.

The only treatment for both unilateral and bilateral cryptorchidism is surgically neutering your dog. Neutering a dog with retained testes is more complicated because it involves locating and removing the testes from the inguinal canal or wherever in the abdomen they may be. While this type of surgery has some risks, it is much safer than not having the surgery. Your dog will will need rest and relaxation for at least two weeks at home.

After going home, your dog will need to be on limited activity with possible cage rest. The veterinarian may also give you an Elizabethan collar for your dog to wear to keep him from licking at the incision area. Check daily for signs of infection at the incision site. The signs of infection are redness, swelling, bad odor, or any kind of discharge. You will have to bring your dog back within 7-14 days to get the stitches removed and to see if it is healing properly. Be sure to tell your veterinarian any concerns you may have.