Cryptorchidism: Retained Testicles in Dogs and Cats

At an early puppy or kitten check, a veterinarian will usually feel gently at the scrotum as part of the routine examination. Most of the time this passes without comment. Occasionally it produces a note in the record saying that one or both testicles cannot yet be felt, and a plan to recheck at the next visit.

That finding — a testicle that has not descended into the scrotum — is called cryptorchidism. It is one of the more common developmental abnormalities in male dogs, less frequent in cats, and it is generally straightforward to manage. But it does matter, because a retained testicle carries real health risks that a normally positioned one does not, and because it has an inherited component that affects breeding decisions.

This article explains how descent normally happens, what a retained testicle means, why removal is recommended, what surgery involves and how recovery goes. It is general information; your veterinarian is the right person to examine your animal and advise on timing and approach.

Important: This article shares general educational information for pet owners and is not a substitute for an in-person veterinary examination, diagnosis, or treatment. For any medical concern or emergency, contact your veterinarian promptly.

How Testicular Descent Normally Works

In male dogs and cats, the testicles form inside the abdomen during development, near the kidneys. Over the period around and after birth they migrate downwards, passing through the inguinal canal in the groin and finally settling in the scrotum. This journey is guided by anatomical structures and hormonal signals working together.

The reason for the trip is temperature. Sperm production requires a temperature slightly lower than core body temperature, which the scrotum provides by sitting outside the body wall. A testicle that remains inside the abdomen sits at full body temperature and does not produce viable sperm, although it continues to produce hormones.

In dogs, descent is usually complete within the first weeks of life and both testicles can typically be felt in the scrotum by around six to eight weeks of age. Some individuals are slower, and a testicle occasionally arrives later. As a general guideline, a testicle that has not descended by around six months of age is unlikely to descend at all — which is why veterinarians usually recheck a few times before concluding anything.

What Cryptorchidism Means

Cryptorchidism simply means one or both testicles have failed to reach the scrotum. Where the retained testicle has stopped determines how it is described and how it is found.

• Unilateral. One testicle is in the scrotum and one is retained. This is the more common pattern in dogs.
• Bilateral. Neither testicle has descended. Affected animals are generally infertile, though they still produce hormones and behave as intact males.
• Inguinal. The retained testicle has reached the groin region and can sometimes be felt under the skin as a small firm structure.
• Abdominal. The testicle has remained inside the abdomen and cannot be felt from outside; locating it may require imaging or surgical exploration.

A related term owners sometimes hear is monorchid, meaning only one testicle exists at all. True monorchidism is rare; in the overwhelming majority of cases, a testicle that cannot be felt is present but retained somewhere along the path it should have travelled.

Cryptorchidism is recognised in all breeds but appears more frequently in some, particularly among smaller and toy breeds. It is considerably less common in cats than in dogs, though it does occur.

Why It Matters: The Health Risks

A retained testicle is not simply an inconvenience or a cosmetic issue. Sitting at body temperature in an abnormal position appears to change the tissue over time, and two specific concerns drive the standard veterinary recommendation to remove it.

The first is tumour development. Retained testicles have a substantially higher likelihood of developing testicular tumours than normally descended ones, and the risk increases with age. Some of these tumours produce hormones, which can cause visible changes elsewhere in the body — symmetrical hair loss, skin changes, enlargement of the mammary tissue or nipples, a pendulous prepuce, reduced interest in normal male behaviours, and in some cases effects on the bone marrow that can become serious.

The second is torsion. A testicle sitting loose within the abdomen can twist on its blood supply, cutting off circulation. This is acutely painful and constitutes a surgical emergency. Signs include sudden severe abdominal pain, a hunched posture, vomiting, reluctance to move and collapse. Any dog with sudden severe abdominal pain needs immediate veterinary attention regardless of cause.

Behaviour and Fertility

A retained testicle still produces testosterone even though it does not produce viable sperm. This means a cryptorchid animal behaves like an intact male: roaming, marking, mounting and intermale tension are all possible, and in cats the characteristically pungent urine of an entire tom is typically present.

An animal with one descended testicle is usually fertile, because the normally positioned testicle functions normally. This surprises some owners who assume that a retained testicle means infertility — it does not, unless both are retained. An unneutered cryptorchid dog can and does sire litters.

Because of the heritable component discussed below, this is a particularly important point for anyone with an intact cryptorchid animal: unintended breeding passes the trait onward, and responsible management means preventing it.

The Inherited Component

Cryptorchidism is widely accepted to have a genetic basis, with the pattern of inheritance appearing complex rather than governed by a single simple gene. Because of this, veterinary and breed organisations consistently advise that affected animals should not be used for breeding, and many breed standards and kennel club regulations disqualify cryptorchid males from the show ring or from registration of offspring.

Since the trait is expressed only in males but can be carried and passed on by females, removing affected males from a breeding programme reduces but does not eliminate its appearance. Breeders who see cryptorchidism recurring in a line generally need to look at both sides of the pedigree rather than at the affected individual alone.

For pet owners, the practical implication is simple. If you have a cryptorchid dog or cat, plan for neutering rather than breeding, and let the breeder know if you obtained the animal from one — that information is genuinely useful to them, and a good breeder will want to hear it.

How the Condition Is Diagnosed

Diagnosis begins with careful palpation. Your veterinarian will feel the scrotum and then work along the inguinal region, since a testicle sitting in the groin can often be felt as a small, firm, slightly mobile structure under the skin. This is easier in a relaxed animal, which is one reason examinations are unhurried and gentle.

If nothing is palpable, the testicle is presumed to be abdominal. Ultrasound is commonly used to locate it before surgery, which helps the surgeon plan the approach and shortens anaesthetic time. In some cases hormone testing is used, particularly where an animal is presented as already neutered but is showing intact male behaviour — a situation that occasionally reveals a retained testicle left behind at a previous surgery.

Rechecking over time is normal in young animals. A veterinarian noting an undescended testicle at eight weeks is not making a diagnosis so much as flagging something to follow, and many will recheck at each vaccination visit before drawing a conclusion.

What Surgery Involves

The recommended treatment is removal of both testicles — the retained one and the normally descended one. Removing only the retained testicle would leave the animal fertile and still able to pass on the trait, which is why complete neutering is standard.

• Scrotal or pre-scrotal. The descended testicle is removed through the routine approach, exactly as in a standard neuter.
• Inguinal. A retained testicle in the groin is removed through a small incision over the site once it has been located.
• Abdominal. An abdominal testicle requires entry into the abdomen, which is a more involved procedure with a longer incision or a keyhole approach where available.
• Laparoscopic. Some practices and referral centres offer minimally invasive removal of abdominal testicles.

Because the procedure is more extensive than a routine neuter, expect a longer anaesthetic, a larger or additional incision, and a higher cost than a standard quote. Ask in advance what approach is planned, what the estimate covers, and whether imaging is included.

Hormonal treatments aimed at encouraging descent are not recommended. They are unreliable, and even where a testicle could be persuaded to move, doing so would mask a heritable trait rather than resolve it.

Timing the Procedure

Timing involves balancing several considerations, and there is no single answer that fits every animal. Neutering age in general is an area where advice has become more individualised in recent years, taking account of breed, expected adult size, joint development and behaviour.

With cryptorchidism, the additional factor is that the risks associated with the retained testicle — particularly tumour development — increase with age. That tends to weigh in favour of not leaving it indefinitely. On the other hand, some veterinarians prefer to wait until an animal is more mature in large breeds, provided reliable steps are in place to prevent breeding in the meantime.

This is a conversation to have specifically with your own veterinarian rather than a decision to make from an article. They can weigh your animal's breed, size, age, temperament and household circumstances and recommend a sensible plan.

Recovery and Aftercare

Recovery from an abdominal cryptorchid neuter resembles recovery from an abdominal surgery rather than from a routine neuter, so expect the restriction period to be taken seriously. Your practice will give specific instructions, and those instructions take precedence over any general guidance.

Contact your veterinary practice promptly if you see significant swelling, discharge, an open wound, worsening pain, repeated vomiting, refusal to eat beyond the first day, or lethargy that deepens rather than improves. These are not situations to monitor overnight and see how things look in the morning.

Questions Worth Asking Your Veterinarian

A short list of questions makes the consultation more productive and helps you understand the plan rather than simply agreeing to it.

1. Where do you believe the retained testicle is, and will imaging be used to locate it beforehand?
2. What surgical approach is planned, and will there be one incision or two?
3. What is the estimated total cost, including imaging, anaesthesia, medication and the recheck?
4. What is the recommended timing for my animal specifically, and why?
5. How long is the restricted activity period, and what exactly counts as restricted?
6. What signs during recovery should prompt me to call rather than wait?

It is also worth asking that the finding be clearly recorded in your animal's history. If you ever move practice or need an emergency clinic, a note confirming that both testicles were removed and where the retained one was found prevents confusion later — particularly in the situation where an apparently neutered animal starts showing intact male behaviour.

Cryptorchidism is, in the end, a manageable finding rather than an alarming one. Identified at a routine check, followed appropriately, and resolved with a well-planned surgery, it rarely causes any lasting difficulty. The risks come from leaving a retained testicle in place indefinitely — which is precisely why that early, unremarkable moment during a puppy or kitten examination is worth paying attention to.