Undescended testicles in dogs – cryptorchidism and treatment

Overview

A retained testicle may lie in the abdomen, in the inguinal canal or beneath the skin between the groin and scrotum. It can remain at different points along its normal route of descent.

In unilateral cryptorchidism, the other testicle is normally positioned in the scrotum. In bilateral cryptorchidism, neither testicle has descended to its correct position.

The estimated frequency of cryptorchidism is about 1–15% of dogs. About 75% of cases are unilateral.

Bilateral cases account for about 25%. A retained testicle beneath the skin in the groin can usually be felt with the fingers.

A retained testicle within the abdomen cannot be felt from outside.

Apart from the missing testicle or testicles, an affected dog usually appears completely healthy.

Causes

Testicles develop in the fetal abdomen near the kidneys, rather than directly in the scrotum. During development, they move through the inguinal canal into the scrotum.

A band of connective tissue called the gubernaculum guides descent. As the puppy develops, shortening of this band draws the testicle towards the scrotum.

Descent may be complete by about ten days of age. Testicles are usually in the scrotum by 6–8 weeks.

The inguinal canal closes at about six months of age. In cryptorchidism, normal descent is disrupted and the testicle remains along its route in the abdomen or groin.

Cryptorchidism is an inherited trait, although the exact pattern of inheritance is not fully understood. Unusually late descent may also be passed to offspring.

Risk factors

Cryptorchidism occurs in all breeds, but small companion breeds may have an increased risk. Small breeds considered predisposed include Toy Poodles, Pomeranians and Yorkshire Terriers.

The condition is also more common in German Shepherds and Siberian Huskies. Bulldogs and other short-muzzled breeds are also affected more often.

Both parents of a cryptorchid male should be considered possible carriers of inherited susceptibility.

Although the abnormality is visible in a male, susceptibility can also pass through the mother. Several cryptorchid males may occur within the same family.

A retained right testicle in the groin is the most common form.

Typical symptoms

• Only one testicle can be felt in the puppy's scrotum.

• In bilateral cryptorchidism, the scrotum remains empty.

• A small testicle may be felt beneath the skin in the groin.

• Your dog may urine-mark or go looking for females even though the scrotum appears empty.

• A testicular tumour may cause hair loss on both sides of the body.

• A tumour may enlarge the testicle in the groin or abdomen.

Cryptorchidism does not usually cause pain or other visible signs of illness before a complication develops.

A hormone-producing tumour can cause female-like changes in a male's sexual characteristics, known as feminisation.

A testicular tumour may also be associated with prostate problems.

A retained testicle is often initially smaller than the normally descended testicle in the same dog.

Complications and consequences

A cryptorchid dog's risk of a testicular tumour has been estimated at at least ten times that of a dog with normally descended testicles. Torsion can block the testicle's blood supply, causing severe pain.

The temperature of a testicle inside the abdomen is too high for normal production of viable sperm. If both testicles remain undescended, the dog is infertile.

A dog with one retained testicle can still make a female pregnant. Among testicular tumours, Sertoli cell tumours in particular may produce excess oestrogen.

About 70% of abdominal Sertoli cell tumours produce hormones. Up to 15% of dogs with an oestrogen-producing Sertoli cell tumour may develop hair loss, anaemia or bone marrow damage.

Most testicular tumours rarely spread to other parts of the body. The outlook is generally excellent when a cryptorchid dog has surgery before complications develop.

Testicular tumours occur particularly in dogs over ten years old. However, cryptorchidism may be associated with a tumour developing in a much younger dog.

Removing the testicle containing the tumour is often curative.

Diagnosis at the vet

Examining the puppy and locating the testicle

The vet palpates the scrotum and groin. A missing testicle may already be suspected during an eight-week-old puppy's examination.

Diagnosis is usually confirmed at six months if the testicles have not descended by then. Descent has been recorded as late as ten months, but descent this late is not normal.

Ultrasound may help locate a retained testicle before surgery. However, not every dog needs ultrasound before removal.

A retained testicle is often smaller than normal, which can make it harder to find. X-rays may also be used to locate it in some cases.

A testicle remaining inside the inguinal canal may neither be felt externally nor seen during abdominal laparoscopy. Before surgery, the vet also establishes whether the missing testicle is on the right or left.

When previous castration is uncertain

Hormone blood tests can establish whether testicular tissue is present when previous castration is uncertain. Anti-Müllerian hormone, or AMH, is usually detectable in a sexually mature dog with testicular tissue.

In a fully castrated dog, luteinising hormone, or LH, is usually high. Complete congenital absence of a testicle is rare in dogs.

If a testicle cannot be found during surgery, subsequent hormone testing can establish whether any testicular tissue remains.

Treatment

Removing the retained testicle

A retained testicle is removed surgically because of the tumour risk. The usual treatment is castration, removing both the retained and normally descended testicles.

A testicle beneath the groin skin can usually be removed through a skin incision over it. Removing an abdominal testicle requires access to the abdomen.

In unilateral cryptorchidism, removal of both testicles may require two skin incisions. If both retained testicles are in the abdomen, they can be removed through the same abdominal incision.

An abdominal testicle can also be removed laparoscopically. Laparoscopy can clearly show the position of the testicles and surrounding structures through small instrument ports.

A testicle in the inguinal canal may require conversion from an attempted laparoscopic procedure to open surgery. Surgery takes place under general anaesthesia, with suitable pain relief planned by the vet.

Local anaesthesia reduces pain both around the wound and during separation of the testicle from its attachments.

Can the normal testicle be preserved?

Preserving a normally positioned scrotal testicle may be considered individually to retain hormone production. This requires that the dog is not used for breeding.

The preserved testicle may also carry an increased tumour risk. It is palpated regularly to detect changes.

The normal testicle must not be removed alone while leaving the retained one inside the body. Hormone treatment has not been shown to make a retained testicle descend reliably.

Surgically moving the testicle into the scrotum is not considered an acceptable solution to an inherited defect. Treatment that preserves the normal testicle may be combined with vasectomy, division of the sperm duct, to prevent reproduction.

Vasectomy removes a short section of the sperm duct, interrupting the route taken by sperm. Sperm have been found in semen for up to 21 days afterwards, so contraception is not immediate.

Discharge and wound healing

The vet prescribes postoperative pain relief and wound care. Some dogs need a protective collar throughout the two-week recovery period to prevent licking.

Licking increases the risk of wound infection. A dog may be sleepier than usual for the rest of the day after surgery and into the following day.

Appetite may be reduced during the first 24 hours. Keep the wound clean and dry and avoid swimming until it has healed.

Running, jumping and boisterous play are restricted because movement strains the healing wound. Initially, outings are short toilet breaks on a lead, as instructed.

Activity is increased gradually according to wound healing and the follow-up examination.

Dissolving stitches beneath the skin do not usually need removal. External stitches or skin staples are removed at the veterinary practice.

Mild redness or bruising can be part of normal healing during the first days after surgery. A small, firm swelling beneath the wound may gradually decrease during recovery.

Adequate energy and protein intake support tissue repair after surgery.

Prevention

Because susceptibility is inherited, a cryptorchid dog should not be used for breeding. Removing a retained testicle prevents tumours and torsion in that testicle.

Removing both testicles also prevents the dog from passing the trait to their own offspring. Some breed registries require the sire's testicular status to be recorded by the time a litter is registered.

Where testicular status is abnormal, some registry rules may allow one litter to be registered with permanent breeding restrictions. Some separate testicular certification schemes require a minimum age of nine months for assessment.

Important for dog owners

Testicular findings from puppy checks and later visits help monitor whether both testicles have descended.

Keep puppy examination records and any previous operation reports. Tell the practice if other males in the family have had retained testicles. If preservation of the normal testicle is planned, agree how it will be monitored and how accidental mating will be prevented.

Some certification schemes record the testicles' status before surgery and the reason for castration in a veterinary certificate.

Some dog-show rules require disqualification when normal testicles are absent, even with a castration certificate.

Under those rules, a castration certificate does not itself prevent entry, although the assessment outcome concerning the testicles is predetermined.

Check the rules of the particular activity for trial and competition participation requirements.

Some participation rules for a male castrated because of illness require previously documented normal testicles and an approved removal certificate.

Check the surgical wound daily for changes.

Photographs help compare its appearance on different days.

Do not apply creams or sprays without the treating vet's explicit instructions.

Calm food puzzles and other gentle enrichment can make daily life easier while exercise is restricted.

Keep normal drinking water available according to the discharge instructions.

A wound check allows assessment of healing and adjustment of the exercise programme.

Passing stools may be delayed for 1–2 days after surgery and anaesthesia.

Frequently asked questions

When is a puppy diagnosed with an undescended testicle?

A missing testicle may be suspected at an eight-week-old puppy's examination. Diagnosis is usually confirmed at six months if the testicle has not descended. Puppy check records and an agreed repeat examination help monitor development. Ultrasound can locate a retained testicle before surgery.

Can a dog with only one descended testicle father puppies?

Yes. If a dog has a functioning, normally descended testicle, they can still make a female pregnant. A cryptorchid dog should not be bred from because of inherited susceptibility. Seeing only one testicle therefore does not provide contraception against an accidental pregnancy.

Must both testicles be removed?

The usual treatment is removal of both testicles. Preserving the normal one may be considered individually. The dog must not then be used for breeding. The preserved testicle is monitored regularly. Discuss this decision with the vet planning surgery. The retained testicle is removed because of the tumour risk.

Is a retained testicle dangerous if there are no symptoms?

Even a symptom-free retained testicle increases the risk of a tumour and torsion. The outlook is generally excellent when surgery takes place before complications develop. Surgery for a dog without symptoms is planned at a routine appointment. Sudden, severe abdominal pain, however, is an emergency. Torsion can cut off the testicle's blood supply.

How do I care for a dog recovering from retained testicle surgery?

Home care includes vet-prescribed pain relief and protection of the wound. A protective collar may be needed for about two weeks. Running and jumping are restricted to allow wound healing. Follow your dog's own discharge instructions and agreed follow-up appointments. Check the wound every day.