Testicular tumours are one of the most common types of tumour in undesexed male dogs

There was just one problem: On initial examination, I could only find his left testicle.

Normally, male dogs have two testicles, located in the scrotum.

Laddie had a condition known as cryptorchidism - where one or both testes fail to descend. As Laddie had one undescended testicle, I diagnosed him with unilateral (one-sided) cryptorchidism.

When neither testicle arrives in the scrotum, it is called bilateral cryptorchidism.

Cryptorchidism is more common in smaller breeds (up to 10 per cent), than in larger breed dogs.

In developing puppies, the testicles gradually relocate from the abdomen, through the inguinal canal (in the inner thigh area) to their final destination in the scrotum by the age of two to eight weeks. Some take as long as six months to get there.

Those that don't make it may be located anywhere along that route - in the abdomen (where they cannot be detected by physical examination), in the inguinal or inner thigh region, or in the area immediately in front of the scrotum.

My examination revealed a mobile, testicular-shaped lump in Laddie's inguinal region.

When they are in the scrotal sac, testicles are at their preferred temperature: several degrees cooler than the core body temperature.

Undescended testes are exposed to higher temperatures. They don't develop like normal testes, tending to be smaller, and may be unable to produce sperm.

You might also like to read:

But the big concern for Laddie is that testicular tumours - one of the most common types of tumour in undesexed male dogs - are about 13 times more likely to occur in cryptorchid testicles.

There are several types of testicular tumour seen in dogs, but cryptorchid dogs are particularly prone to sertoli cell tumours. These can cause life threatening bone-marrow suppression.

Cryptorchid dogs are also at increased risk of testicular torsion, an excruciating condition where the testicle rotates, twisting and cutting off blood supply to the testicle. This requires emergency surgery.

Cryptorchidism is an inherited condition. As there is currently no commercially available test for the gene(s) responsible (Blades et al., 2022), the consensus is that affected dogs should not breed, as their offspring are likely to have the same condition.

Treatment involves the removal of the affected testicle through desexing.

For Laddie, this would involve removing the scrotal testicle through a small pre-scrotal incision, as we would in a routine desexing procedure.

Removal of viable testes would stop him from breeding and passing on the condition. However, it would also involve an additional incision being made over the undescended testicle - to confirm it is indeed a testicle and not fat or a lymph node - to remove it.

For dogs with abdominal testes the procedure requires opening the abdomen to locate and remove the undescended testicle/s. This is a bigger and slightly more complex surgery.

Nonetheless, removing undescended testicles is recommended to prevent testicular cancer and testicular torsion.

Laddie's owners have made the decision to have both testes removed, so neither they nor Laddie will have to worry about these conditions in the future.