Cryptorchidism
Undescended Testicles
Original source and elaborated description with graphical imagery is HERE
below is a snippet for the main points and questions that get asked of me.
Cryptorchidism is defined in most textbooks as a failure of normal testicular descent. In the dog, the definition has been further refined and canine cryptorchidism is defined as the condition whereby one or both testicles are not present within the scrotal sac of the canine animal by the age of 8 weeks. The term encompasses situations whereby the testicles are still located within the male animal's abdominal cavity and also situations whereby the testicles have exited the animal's abdomen, but are residing in the animal's inguinal ring (inguinal canal) or regions underneath the skin, lateral to the penis and just cranial to (ahead of) the scrotal sac.
Some textbook sources say that you can not 100% diagnose a pet cat or dog as being cryptorchid until it has reached puberty: 6 months for cats and smaller dog breeds and around 12 months for large breeds (theoretically, puberty occurs at around 18 months for giant breeds, but they rarely get the condition anyway). Certainly if the animal gets to 1 year of age (which should be prior to that male animal being permitted to breed anyway) and has not dropped, then it should be considered exceedingly unlikely to. In fact, most textbooks claim that if the animal has not descended by 2 months (8 weeks) of age then it is very unlikely to, however, because you do occasionally come across the rare individual animal that drops late, some of these texts do permit the puberty age cut off.
In canine puppies, the process of testicular decent normally occurs shortly after birth (within 5-10 days of birth) and most male pups will have readily palpatable testicles within their scrotal sacs at around 10-14 days of age. I have found that most male puppies have readily palpatable testicles in their scrotum sacs by the time of first vaccination (6-8 weeks).
Because the gubernaculum (see section 1a) may not be fully receded and contracted down in some 6-7 week-old pups, it is likely that these testicles will still be mobile and able to slide back and forth between the puppy's abdomen and scrotum. Puppies will often retract these mobile testicles into their abdominal cavities when they are excited or anxious (e.g. they are often excited or nervous at vaccination time). As a result, some pups aged 6-7 weeks and earlier are wrongly diagnosed as being cryptorchid (retained testicles) because their retractile testes are being sucked up (retracted) into their abdominal cavities during excitement. The gubernaculum generally recedes (shrinks) fully, preventing the movement of the testicle from the scrotum to the abdominal cavity or inguinal canal, by about 8 weeks of age and, after this point, the testes are either palpable within the scrotal sac or they are considered retained (cryptorchid) - see section 3 for more details on the timing of testicle descent with regard to the diagnosis of true cryptorchidism.
Author's note: You will occasionally get some pups who, at 8-10 weeks of age, will still be exhibiting slight testicular movement: they will be able to pull their testicles forwards, alongside the penis, when stressed or excited. These pups should be able to drop their testicles back into their scrotum when relaxed and it should not be difficult for the vet to manually manipulate the testicles back into the correct scrotal position during the examination. Testicles that are difficult to move back into place should be suspected of having cryptorchidism.
Author's note: The timing of testicular descent has not been studied in every individual breed of dog. There may be some breed variation in the timing of testicular descent. For information on the testicular descent of individual breeds, it may be best to look up a specific breed site or ask a couple of dog breeders who breed that kind of animal.
Some textbook sources say that you can not 100% diagnose a pet cat or dog as being cryptorchid until it has reached puberty: 6 months for cats and smaller dog breeds and around 12 months for large breeds (theoretically, puberty occurs at around 18 months for giant breeds, but they rarely get the condition anyway). Certainly if the animal gets to 1 year of age (which should be prior to that male animal being permitted to breed anyway) and has not dropped, then it should be considered exceedingly unlikely to. In fact, most textbooks claim that if the animal has not descended by 2 months (8 weeks) of age then it is very unlikely to, however, because you do occasionally come across the rare individual animal that drops late, some of these texts do permit the puberty age cut off.
In canine puppies, the process of testicular decent normally occurs shortly after birth (within 5-10 days of birth) and most male pups will have readily palpatable testicles within their scrotal sacs at around 10-14 days of age. I have found that most male puppies have readily palpatable testicles in their scrotum sacs by the time of first vaccination (6-8 weeks).
Because the gubernaculum (see section 1a) may not be fully receded and contracted down in some 6-7 week-old pups, it is likely that these testicles will still be mobile and able to slide back and forth between the puppy's abdomen and scrotum. Puppies will often retract these mobile testicles into their abdominal cavities when they are excited or anxious (e.g. they are often excited or nervous at vaccination time). As a result, some pups aged 6-7 weeks and earlier are wrongly diagnosed as being cryptorchid (retained testicles) because their retractile testes are being sucked up (retracted) into their abdominal cavities during excitement. The gubernaculum generally recedes (shrinks) fully, preventing the movement of the testicle from the scrotum to the abdominal cavity or inguinal canal, by about 8 weeks of age and, after this point, the testes are either palpable within the scrotal sac or they are considered retained (cryptorchid) - see section 3 for more details on the timing of testicle descent with regard to the diagnosis of true cryptorchidism.
Author's note: You will occasionally get some pups who, at 8-10 weeks of age, will still be exhibiting slight testicular movement: they will be able to pull their testicles forwards, alongside the penis, when stressed or excited. These pups should be able to drop their testicles back into their scrotum when relaxed and it should not be difficult for the vet to manually manipulate the testicles back into the correct scrotal position during the examination. Testicles that are difficult to move back into place should be suspected of having cryptorchidism.
Author's note: The timing of testicular descent has not been studied in every individual breed of dog. There may be some breed variation in the timing of testicular descent. For information on the testicular descent of individual breeds, it may be best to look up a specific breed site or ask a couple of dog breeders who breed that kind of animal.
