The definition of cryptorchidism is “the failure of one or both testicles to descend into the scrotum.”
The condition is caused by a genetic fault and is passed on from father to puppy (or kitten). For this reason, cryptorchid animals should not be used for breeding.
Having a retained testicle has health implications for the animal. Testicles are designed to be kept slightly cooler than body temperature (hence sitting in the scrotum). Because a retained testicle is warmer than intended, there is an increased risk of cancerous change (both in the retained and the scrotal testicle).
Another risk is a testicle in the abdomen is more prone to “rattle around” and may flip over on its blood supply in a serious condition called testicular torsion.
The most obvious symptom is only 1 testicle being present in the scrotum.
Your veterinarian checks male pets at the time of vaccination and will tell you if a testicle has not yet descended. However, although it is usual for the testicles to be in the scrotum at 8 weeks of age, for some pets it just takes longer, and it is fair to wait until the puppy or kitten is 6 months old before concluding he is cryptorchid.
The Rottie mentioned earlier was cryptorchid, but his human brought him in for a different problem (or so he thought) because the dog had suddenly become very unwell. When I checked the dog’s tummy, I could feel a grapefruit-sized lump, which was tender and painful.
Long story short, the dog was taken to theater, where I discovered his retained testicle had flipped over and cut off its own blood supply. The strangulating testicle had swollen to about five times its regular size — no wonder the poor chap was sore!
This is a genetic condition that affects up to 15% of male dogs. Statistically, 75% of cases affect 1 testicle, of which it is twice as likely that the right is retained rather than the left.
The reason the testicle doesn’t come down into the scrotum is a failure of a fetal ligament to contract and pull the testicle through the tummy out of the inguinal canal and into the scrotum.
Most normal dogs are equipped with a pair of scrotal testicles by 8 weeks old, but in some dogs it does take up to 6 months. The errant testicle can be located anywhere from the skin of the inner thigh to the inguinal canal, or it may be fully retained within the abdomen.
A diagnosis is made by feeling the scrotum. However, this is not quite as foolproof as it sounds.
If for any reason the dog was castrated and only the scrotal testicle was removed, it can appear that the cryptorchid is fully neutered even though he has a functional testicle hidden in the abdomen that is pushing out testosterone. In these cases, a blood test measuring testosterone should hint at the problem.
In this video, a dog named Pikachu has the condition:
Cryptorchid dogs should always be neutered — this includes removing both the scrotal and retained testicle.
Research has shown that if 1 testicle is retained, the normal testicle is also at greater risk of becoming cancerous. And, of course, a retained testicle may twist and cut off its blood supply, and the dog or cat may suddenly become seriously ill.
Because of the inherited nature of this condition, affected animals should not be bred from and should be neutered.
- “Incidence of cryptorchidism in dogs and cats.” Yates, Hayes, Heffernan & Beynon. Vet Rec, 152: 502–504.
- “Canine cryptorchidism.” Romagnoli. Vet Clin North Am Small Anim Pract, 21(3): 533–544.
This pet health content was written by a veterinarian, Dr. Pippa Elliott, BVMS, MRCVS. It was last reviewed March 1, 2017.