Neutered or not dropped? All about retained testicles in cats

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When a cat arrives at a cat rescue charity for rehoming, one of the first questions we ask is: is this cat neutered? For cats with a clear veterinary history, the answer is simple. But when dealing with strays or abandoned cats, it’s not always obvious. Male cats present a particular challenge if we think they might have a condition called cryptorchidism, or “retained testicles.”

In this article, we’ll explore what cryptorchidism is, how it affects cats, and how to tell the difference between a truly neutered male and one whose testicles simply never descended.

What is cryptorchidism?

Cryptorchidism is the medical term for a condition where one or both testicles fail to descend into the scrotum. In a normal male kitten, the testicles develop inside the abdomen and gradually move down into the scrotal sac by a few months of age. When this process doesn’t happen, the testicle may remain lodged in the abdomen or stop somewhere along the inguinal canal (the passageway between the abdomen and the scrotum).

Unilateral cryptorchidism: only one testicle has descended; the other is retained.

Bilateral cryptorchidism: neither testicle has descended.

This condition is relatively uncommon in cats compared to dogs, and studies tell us that only somewhere around 2% of male cats will be affected. But when it does occur, it can complicate decisions in rehoming centres and vet clinics alike.

Why does it matter?

You might wonder why retained testicles matter, especially if the cat is otherwise healthy. There are three main reasons:

Fertility:

A cryptorchid cat can still be fertile. If a testicle is present somewhere in the body but never properly descended, it may still produce viable sperm, meaning the cat can father kittens. This depends on where it comes to rest – research suggests that the closer to the skin the testicle is, the more likely it is to retain some function.

Health risks:

Retained testicles are prone to serious problems, including testicular cancer and torsion (twisting of the spermatic cord, which is painful and potentially life-threatening).

Behaviour:

Cats with retained testicles still produce testosterone. This means they may spray urine, fight, and roam. These are behaviours most owners hope neutering will reduce.

For these reasons, a cryptorchid cat is considered not neutered until both testicles are surgically removed.

The challenge of strays and unknown histories

In rescue and rehoming charities, many cats arrive without any medical records. A male cat may have no visible testicles, but does that mean he has been neutered? What if it means his testicles never descended in the first place?

This distinction is crucial. Rehoming a cat who still has functioning testicles (hidden in the abdomen) could lead to accidental breeding, unwanted litters, and health risks for the cat.

How to tell the difference: Neutered vs. Cryptorchid

1. Physical examination:

The first step is always for a vet to carry out a careful physical examination. Neutered males usually have a small surgical scar near the scrotum or inguinal area, though it can fade with time. Their scrotum will be empty and shrunken, with no palpable tissue inside. Cryptorchid males may have an underdeveloped scrotum, but no surgical scars. Sometimes, one testicle can be felt in the groin region, even if it hasn’t dropped fully.

However, scars can be difficult to see in older strays, and palpation isn’t always reliable—especially for abdominally retained testicles.

One trick of the trade is to check for penile spines.

Intact male cats naturally develop tiny, backward-pointing barbs (spines) on the surface of the penis. These are hormonally driven by testosterone and play a role in stimulating ovulation during mating.

Penile spines are present in intact males, including those with retained testicles, because they are still producing testosterone. After castration, the spines regress and usually disappear within about six weeks as testosterone levels fall.

It’s a relatively non-invasive procedure to check for the presence of penile spines, but it is best done by a veterinary professional so that minimal stress is caused for the cat.

If spines are present, this usually indicates that the cat is producing testosterone, so he is not fully neutered. This could be due to being entire or cryptorchid.

If penile spines are absent, the cat is likely neutered, or possibly a late-developing young kitten who hasn’t yet reached puberty.

For rehoming charities, checking for the penile spines can be a quick and practical tool when assessing new arrivals. While not 100% definitive on its own, it’s a strong indicator when combined with other evidence.

2. Behavioural clues:

A neutered male cat typically has reduced sexual behaviours. But behaviour alone isn’t a reliable indicator, as some neutered males may still spray or be territorial, while some intact cats are more laid back. Male cats with functioning testicles tend to have a strong scent to their urine (a distinctive ‘tomcat smell’). If they’ve been under the influence of testosterone for long enough, male cats also develop a chunkier build, with a wider, more solid-looking head and face. They may have scars and scratches on their head or body from fighting with other male cats.

3. Hormone testing:

Vets can run a blood test to check testosterone levels. A cat that has been fully neutered will have very low testosterone, while one with retained testicles will usually show measurable amounts. However, testosterone levels may vary, and a low level may be present in an entire adult male as well as in young entire males which have not yet reached puberty.

The hCG (human chorionic gonadotropin) stimulation test is another option. This involves giving the cat an injection that stimulates testosterone release, then measuring the levels in the blood. A rise in testosterone confirms the presence of testicular tissue. But there is still a risk that the test might not work well for young entire males which have not yet reached puberty.

4. Ultrasound imaging:

An abdominal ultrasound can sometimes locate retained testicles inside the body. This is especially useful for cats with bilateral cryptorchidism, where no testicles are visible at all.

5. Exploratory surgery:

If, after careful consideration of the evidence, the vet feels a retained testicle is present, the cat will need to undergo surgery to search for it. If no testicle is found, the cat was likely neutered after all. However, if there is a suspicion of a retained testicle, then surgery is indicated in order to remove it.

Treatment for cryptorchid cats

The only effective treatment for cryptorchidism is surgery. Standard castration involves making a small incision in the scrotum to remove the testicles. For cryptorchid cats, however, the procedure may involve additional small incisions:

If the testicle is lodged in the inguinal canal, the vet will make an incision there.

If it is retained in the abdomen, abdominal surgery is required.

Once both testicles are removed, the cat is considered fully neutered. This eliminates fertility, reduces hormone-driven behaviours, and prevents the health risks associated with retained testicles.

Frequently asked questions

Can a cat with only one descended testicle still reproduce?

Yes, it’s possible. Even with one retained testicle, the descended one may be fertile. It’s also sometimes possible for the retained testicle to stay fertile too. This is another reason why it’s not recommended to only remove the descended testicle and to leave the undescended one behind.

Will cryptorchidism fix itself as the cat ages?

No. If the testicle hasn’t descended by 6 months of age, it won’t. Surgery is the only solution.

Is cryptorchidism hereditary?

Yes, there is likely a genetic component. This is another reason why affected cats should not be bred.

Can cryptorchid cats still spray after surgery?

Once both testicles are removed, testosterone levels drop, and behaviours like spraying usually reduce, though it can take weeks to months. Some cats may continue spraying out of habit or because of stress rather than hormones.

Key Takeaways

Cryptorchidism is the medical term that means retained testicles, a condition where one or both testicles fail to descend into the scrotum.

Cats with retained testicles are not neutered and may still reproduce.

Physical examination to look for the presence of penile spines is a good, non-invasive way to check whether a cat may be cryptorchid.

Hormone testing, ultrasound, and exploratory surgery can also help distinguish cryptorchid cats from neutered ones.

Surgery is essential to remove retained testicles and prevent health issues.

For rescues and shelters, it’s important not to assume absence of testicles means a cat is neutered; always confirm before rehoming.

Final Thoughts

Understanding cryptorchidism is vital for anyone working with cats of unknown history. Whether you’re a vet, a shelter worker, or a new adopter, knowing how to spot the difference between a neutered male and one with retained testicles helps protect feline health, prevent unwanted litters, and ensure every cat goes to their new home in the best possible condition.