Now I know what you are thinking. In order to answer that, we need some background knowledge about testicular development. The testicles arise from cells within the abdominal cavity, and then descend into the scrotum early in life. Frequently this descent is complete at birth. Failure of one or both testicles to descend normally by the age of four months is diagnostic for cryptorchidism.
Cryptorchidism is thought to be an inherited defect, and can be seen in any breed.
My experience has shown it to be more common in the small and toy breeds. The literature reports higher than normal incidence of cryptorchidism in Pomeranians, Toy Poodles, and Yorkshire Terriers. Diagnosis of cryptorchidism is straightforward and based on physical examination findings. A subcutaneous testicle can usually be palpated, the same is not true for one retained within the abdomen. Interestingly enough, the right testicle is twice as likely to be retained as the left.