What Cryptorchidism Means
Cryptorchidism refers to the failure of one or both testicles to descend into the scrotum by the time a puppy reaches sexual maturity. The word comes from the Greek for "hidden testicle," which describes the condition precisely: the affected testicle remains somewhere along the normal path of descent — either within the abdomen or in the inguinal canal — rather than reaching its final scrotal position.
The condition is among the most common congenital abnormalities seen in male dogs. Prevalence estimates vary by study and breed, but figures typically range from 1 to 4 percent of the general dog population, with considerably higher rates in certain breeds. It can affect one testicle, known as unilateral cryptorchidism, or both, known as bilateral cryptorchidism. Unilateral cases, with the right testicle more commonly affected, are significantly more frequent than bilateral ones.
How Testicles Normally Descend
In a normally developing male dog, both testicles begin their life near the kidneys within the abdominal cavity. Under the influence of hormonal and mechanical signals, they migrate progressively downward through the inguinal canal and into the scrotum. This process is typically complete by six to eight weeks of age, though in some breeds it may take slightly longer — up to four to six months in certain cases.
If a testicle has not descended by the time the dog is six months old, it is considered unlikely to do so. Waiting and hoping for late descent beyond this point is generally not warranted, and management decisions should begin.
The Genetics Behind the Condition
Cryptorchidism is considered a heritable condition, though the exact mode of inheritance is complex and not fully characterised. It is thought to involve multiple genes rather than a simple dominant or recessive pattern.
Breeds with notably elevated rates include Chihuahuas, Toy and Miniature Poodles, Yorkshire Terriers, Dachshunds, Boxers, Siberian Huskies, and Shetland Sheepdogs, among others. The hereditary nature of the condition has important implications for breeding decisions — affected dogs should not be bred, as this perpetuates the genetic risk in subsequent generations.
Why Retained Testicles Are a Serious Health Risk
The scrotum is not simply a location of convenience for the testicles. Its external position keeps the testes at a temperature approximately 2 to 4 degrees Celsius below core body temperature, which is essential for normal sperm production. A retained testicle, exposed to the warmer environment inside the abdomen or inguinal canal, is unable to produce viable sperm. In bilateral cases, this means the dog is infertile.
More critically, the retained testicle faces a dramatically elevated risk of neoplastic transformation. Research consistently shows that cryptorchid testicles are 9 to 14 times more likely to develop cancer than normally descended testicles. The most common tumour types are Sertoli cell tumours, seminomas, and interstitial cell tumours.
Sertoli cell tumours are of particular concern because they can produce oestrogen, leading to a syndrome of feminisation. Affected dogs may develop enlarged nipples, attraction of other males, a pendulous prepuce, and bone marrow suppression. The bone marrow changes can cause life-threatening anaemia and are one of the most serious complications associated with cryptorchid malignancy.
Retained testicles are also susceptible to testicular torsion — a twisting of the spermatic cord that cuts off blood supply. In a mobile, intra-abdominal testicle, torsion can occur suddenly and causes severe abdominal pain. It is a genuine surgical emergency.
Diagnosis
Diagnosis is made primarily through physical examination. Both testicles should be palpable in the scrotum during a standard health check. If only one or neither is present, the vet will attempt to palpate the inguinal region to locate the missing testicle. Inguinal testicles are often palpable just beneath the skin in this region.
When a testicle cannot be felt externally at all, ultrasonography is the most useful next step. Abdominal ultrasound can usually locate an intra-abdominal testicle, assess its size and appearance, and identify any suspicious changes that might suggest early malignancy. In difficult cases, more advanced imaging may be required.
Treatment: Why Surgery Is Always Recommended
The treatment for cryptorchidism is surgical removal of the retained testicle or testicles. This is not an elective recommendation in the conventional sense — it is a genuine medical necessity given the cancer risk.
The surgical approach depends on where the testicle is located. An inguinal testicle requires a relatively straightforward procedure similar to routine castration. An intra-abdominal testicle requires an abdominal approach, which is a more involved surgery but one that experienced surgeons perform routinely.
If the dog is not intended for breeding, the normally descended testicle is typically removed at the same time, completing the full castration. This also eliminates any residual testosterone-driven behaviours and prevents the retained testicle's hormonal output from continuing.
Some owners ask whether the retained testicle alone can be removed while leaving the normally descended one in place, maintaining fertility. In principle this is possible, but given the hereditary nature of the condition, breeding such a dog is ethically problematic and is not generally recommended by veterinary or breed association guidelines.
What Owners Should Watch For
Puppies should have their testicles checked by a vet at their initial vaccination appointments. If both are not present by the time the puppy is four to six months old, follow-up palpation and potentially ultrasound should be arranged. Early identification allows timely planning for surgical management.
In an older dog diagnosed with cryptorchidism, particular vigilance is warranted for the signs of Sertoli cell tumour-related feminisation or sudden abdominal pain consistent with testicular torsion. Any of these presentations should prompt immediate veterinary attention.
Cryptorchidism is one of those conditions where the risk is invisible until it is not — and when malignancy or torsion strikes a retained testicle, it can do so quickly. Understanding the anatomy, the risks, and the clear case for surgical management puts owners in the best position to protect their dog's health over the long term.