Cryptorchidism

I have seen plenty of spays and neuters at the clinic.  They are a routine, daily occurrence so it is always interesting when something out of the ordinary happens during one of these procedures.  The other day there were two neuters scheduled, a cat and a dog.  Nothing too exciting or out of the ordinary.  However, while the animals were being prepped for surgery it was noticeable that something was not quite right.  Both animals had only one testicle.  They were both exhibiting cryptorchidism, otherwise known as retained testicles.  Cryptorchidism is a condition in which a male's testicles have not descended into the scrotum.  During male fetal development, the testes develop high in the abdomen and move from the abdomen down through the inguinal canal and into the scrotum.  By the time an animal is at the right age to be neutered, the testes should be fully descended.  If they fail to descend, the testicles may remain in the abdomen or inguinal canal.  Cryptorchidism can be unilateral in which one testis is retained (like the two neuters scheduled for surgery at the clinic), or it can be bilateral in which both testes are retained.  Due to the need for thermal regulation during sperm production, bilateral cryptorchids are sterile while unilateral cryptorchids are still fertile.  Cryptorchidism is considered to be an X-linked, autosomal-recessive trait, or in other words a heritable defect, so it is highly advised that cryptorchid animals should not be used for breeding.  Surgical removal is the only treatment for cryptorchidism.  A cryptorchid surgery is more complicated than a normal neuter because it is more invasive (usually involves opening the abdomen) and the cryptorchid testicle may be difficult to locate.  Even animals that are unilateral cryptorchids should have both testicles removed because the retained testicle is prone to testicular torsion and testicular cancer.