Cryptorchidism in cats is a condition where one or both testicles fail to drop into the scrotum. The word literally means “hidden testicle.” It’s the most common reproductive disorder in male cats, affecting roughly 1.3% to 6.2% of the population depending on breed. If your cat was supposed to be neutered and the vet couldn’t find a testicle, or if your male cat still acts intact despite appearing neutered, cryptorchidism is likely what you’re dealing with.
How Testicular Descent Normally Works
In kittens, the testicles form inside the abdomen near the kidneys and gradually migrate downward through a narrow passage called the inguinal canal into the scrotum. This process should be complete by around six months of age. Veterinarians generally wait until that point before officially diagnosing a kitten as cryptorchid, since some testicles are simply slow to arrive. After six months, a testicle that hasn’t descended on its own almost certainly won’t.
A retained testicle can stop at different points along the migration path. Some get stuck inside the abdomen, while others make it partway and lodge in the inguinal canal (the passage through the groin). Where the testicle ended up matters because it determines the complexity of surgery later.
Unilateral vs. Bilateral Cryptorchidism
Most cryptorchid cats, between 78% and 90%, have only one retained testicle. This is called unilateral cryptorchidism, and the left and right sides are affected equally. The other testicle sits in the scrotum normally and functions as expected, which means these cats still produce testosterone, are still fertile from the descended testicle, and still behave like intact males.
Bilateral cryptorchidism, where both testicles are retained, is less common. These cats typically can’t reproduce because the higher body temperature inside the abdomen impairs sperm production. They do still produce testosterone, though, so they’ll display all the hormonal behaviors of an unneutered male.
Breeds at Higher Risk
Cryptorchidism has a genetic basis. It’s classified as a disorder of sexual development tied to the XY chromosome pair. Persian and Ragdoll breeds appear to have the highest incidence, though it occurs in mixed-breed cats as well. In some cases, cryptorchidism is linked to more complex chromosomal conditions. Male cats with three coat colors (calico or tortoiseshell patterns) almost always carry an extra X chromosome, and these cats frequently have cryptorchidism alongside other reproductive abnormalities. Tricolored males are rarely fertile regardless of whether their testicles descend.
Because of the hereditary component, breeding from cryptorchid males or their close relatives passes the trait to future generations. Responsible breeders remove affected cats from their programs.
Signs Your Cat May Be Cryptorchid
The most obvious physical sign is a scrotum that feels empty on one or both sides. But many cat owners don’t regularly check, so behavioral clues are often what raise suspicion first. A cryptorchid cat still produces testosterone, so even if a previous owner or rescue organization reported the cat as neutered based on an empty scrotum, the cat will act intact.
Behaviors to watch for include urine spraying, strong-smelling urine, mounting other cats, territorial aggression, and roaming. If your cat was supposedly neutered but still displays these behaviors persistently, a retained testicle could be producing the hormones driving them. This is one of the most common scenarios that brings owners to search for this condition: a “neutered” cat that clearly isn’t behaving like one.
How Vets Confirm the Diagnosis
A physical exam is the starting point. Your vet will palpate the scrotum and the inguinal area to feel for a testicle that may be lodged in the groin. Testicles retained deeper in the abdomen can’t be felt from outside, so additional testing is needed.
The most reliable blood test measures a hormone called anti-Müllerian hormone, or AMH. A positive result confirms that testicular tissue is present somewhere in the body, while a negative result is consistent with a fully castrated cat. This test works even in young cats before they reach sexual maturity, which gives it an advantage over testosterone testing. Testosterone levels in cats fluctuate with the seasons, dropping in fall and winter, which can produce misleading results.
When seasonal testosterone dips make a simple blood draw unreliable, vets can use a stimulation test. A hormone injection prompts any remaining testicular tissue to ramp up testosterone production, and a blood sample taken two hours later reveals whether the tissue is there. Ultrasound can also help locate a retained testicle inside the abdomen or inguinal canal, especially when planning surgery.
Why Removal Is Necessary
Retained testicles don’t just cause unwanted behaviors. A testicle trapped inside the abdomen sits at a higher temperature than nature intended, and over time this increases the risk of testicular cancer. The tissue can also twist on itself, a painful emergency called testicular torsion. For these reasons, surgical removal is strongly recommended for every cryptorchid cat, not optional.
What Surgery Looks Like
The surgical approach depends on where the testicle is located. If the retained testicle is in the inguinal region, the vet makes an incision over the inguinal ring in the groin and follows the cord-like structures that normally guide the testicle during development. This approach works well for testicles that made it partway through the canal but stopped short of the scrotum.
For testicles retained deeper in the abdomen, the surgeon needs to open the abdominal cavity. This can be done through a traditional incision or, at specialty practices, through laparoscopic surgery using small camera-guided instruments. Laparoscopy involves smaller incisions and typically a faster recovery, but it requires specialized equipment and training that not every clinic offers.
If your cat is a unilateral cryptorchid, the descended testicle is removed at the same time through a standard neuter incision. Recovery from a straightforward inguinal approach is similar to a regular neuter, usually a week or so of restricted activity. Abdominal surgery requires a slightly longer recovery period, closer to 10 to 14 days, since the incision is deeper. Once both testicles are removed, testosterone production stops completely, and intact male behaviors like spraying and aggression typically fade over the following weeks to months.
What to Expect After Surgery
Hormone-driven behaviors don’t vanish overnight. Testosterone clears the bloodstream within a few days, but habits that a cat has practiced for months or years may persist as learned behavior even after the hormonal driver is gone. Urine spraying, for instance, resolves in most cats after neutering but can continue in some, particularly if the cat was cryptorchid for a long time before surgery. The younger the cat is at the time of removal, the less likely these behaviors are to become entrenched.
The retained testicle is typically sent for examination by a pathologist to check for any cancerous changes, especially in older cats who lived with the condition for years. In most cases, particularly in younger cats, the tissue comes back normal and no further treatment is needed.