Cryptorchidism

What is Cryptorchidism?

The process of testicular development and descent into the scrotum in the embryonic and neonate in young puppies and kittens.

Cryptorchidism is the result of failure of normal testicular descent into the scrotum.

To understand what cryptorchidism is one must understand how the Testicle forms early in embryonic life and then descends into the scrotum during late foetal life- in  the womb or early neonatal life- soon after birth. (short version)

Cryptorchidism is not caused by any failure of testicular formation, however it is the result of failure of descending into its proper placement. Testicles and ovaries are formed when the animals kidneys are developing and it is during the last stage of development these organs called mesonephron that results in a mature functioning testicle.

The testicle, now large and formed will start to hang from the abdominal cavity by mesenteries - membranes - similar to the intestine. The testicle will slowly start to migrate towards the animal's rear being pulled caudally by the gubernaculum - tight band of connective tissue, which links one end of each testicle to the region underneath the animals perineal skin. In order for the sperm to be fertile for reproduction the testicles must relocate to a cooler site within the animal's hot body. They must relocate to a special testicle-holding pouch that sits right behind and under the skin of the penis, which is called the scrotum.

This process is called testicular descent. The path of the gubernaculum (band), from the testis (gonads) to the scrotal site, passes through a hole - the inguinal canal - in the muscular wall of the animal's abdominal cavity, somewhere in the region of the animals groin area. The role of the gubernaculum is to contract and draw the testis from the abdominal cavity through the inguinal canal and into the scrotal sac. During this process, some of the lining of the abdominal cavity also gets dragged into the scrotal sac along with the migrating testis.

So, What exactly is occurring between the migration to where the testicles do not transition to their final destination, the Scrotum?

Knowing that much of the scrotum is essentially continuous with the animal's abdominal cavity is important:

1. It explains why a cryptorchid or undescended testicle can be discovered.
2. It also explains why some animals develop scrotal or inguinal hernias - called testicle hernias.

When the gubernaculum finishes its contraction, having drawn the testis into the scrotal sac, it completely regresses - shrivels up to just a small bleb of scar tissue that resides at the bottom of the testicle. Prior to complete regression, it is possible for the testicle to slide back and forth between the abdomen and the scrotal region, but after gubernaculum regression, the testicle is fixed within the scrotal sac and therefore unable to move out of it.

In canine puppies, the process of testicular descent normally occurs shortly after birth - within 5-10 days of birth - and most male pups will have readily palpable testicles within their scrotal sacs at around 10-14 days of age. It has been notated that "most" male puppies have readily palpable testicles in their scrotum by the time they reach 8 weeks old. Because the gubernaculum may not be fully receded and contracted down in some pups, it is likely that their testicles will still be mobile and able to slide back and forth between the puppy's abdomen and the scrotum.

Puppies will often retract their testicles back into their abdomen when "excited or nervous", as a result, some pups aged 8 weeks and earlier are wrongly diagnosed as being cryptorchid. The timing of testicular descent has not been studied in every individual breed of dog and there are some breed variations in the timing of testicular descent.

Cryptochidism is defined in most textbooks as a failure of normal testicular descent. In the dog, the definition has been refined and is a condition whereby one or both testicles are not present within the scrotal sac of the animal by the age of 8 weeks. Some textbooks say that you can not 100% diagnose a dog or cat as being cryptorchid until it has reached puberty:

• 6 months for cats and smaller dog breeds
• ​12 months for large breeds
• 18 months for giant breeds

​It is stated that certainly by the age of 1 year old - if the animal's testicles have not descended by that age, then it should be considered that they unlikely will. The reason is that occasionally you will come across the rare dog or cat that descends late.

Cryptorchidism is divided into two subgroups:

1. Unilateral - is the condition whereby only one testicle is within the scrotal sac, but the other one is undescended. Unilateral is easier to diagnose and most common.
2. Bilateral - is the condition whereby neither testicle is within the scrotal sac, both are undescended.​​

Conditions that are sometimes confused with cryptorchidism:

1. Anorchism - is the condition whereby a male animal has been born completely without testicles.
2. Monorchism - is the condition whereby a male animal has been born with only one "single" testicle.

​​Both Anorchism and Monorchism are very rare in comparison to Cryptorchidism.

Conclusion:
It is recommended by veterinarian's that an animal that has not had the descending of the testicles by 1 year for a small dog breed and 18 months for a large dog breed, then that dog should be neutered because the undescended testicle or testicles can become twisted, which is painful and/or develop cancer from the heat of the core body temperature of the dog itself.