This article will help you
better understand the developmental abnormality of cryptorchidism, or
undescended testicles in male puppies. If your pet is showing any
symptoms or signs of disease, please contact your veterinarian. We want
you and your pet to be happy and healthy.
This condition may be
inherited or present from birth. Cryptorchids should not be bred,
problem is believed to be hereditary. The testes start life within the
abdomen, near the kidneys, and then drop down into the scrotum at
around the time of birth. Though newly weaned puppies sometimes
have only one, or sometimes no testes present, usually two testes are
present between two
months and six months of age. If they have not appeared by this
stage, they are
unlikely to drop. They may be just under the skin near the scrotum or
in the abdomen and are known as retained testicles. A cryptorchid will
often have no problems
initially with his
situation, showing no indications of being in pain or discomfort.
research has shown that retained testicles often run a greater risk of
becoming cancerous and a malignant tumour is more common. Being
inside the abdomen, these tumours are also more likely to go
Some also feel that there is an increased risk of testicular torsion,
is very painful. In some breeds dogs have lived very long lives
being castrated but these seem to be the exception rather than the rule. When castrating, both testicles
be removed as, though
do not always produce sperm, they are more likely to develop testicular
For these reasons you should have your dog castrated.
What is Cryptorchidism?
Cryptorchidism (undescended testicles)
Counting to Two
During development before
birth, the testicles migrate from the abdomen into the scrotum.
Normally this is complete by 10 days of age. Cryptorchidism means that
one or both of a dog's testicles have not descended into the scrotum.
If this does not
happen by 8 weeks, the dog is generally diagnosed as cryptorchid,
although the testicles may still descend up to 4 months or so.
How is cryptorchidism inherited?
Although the condition is of course seen only in male dogs, both males
and females can carry the gene for cryptorchidism. Heterozygous males
and females, and homozygous females, will be physically normal, but can
pass the gene on to their offspring. Homozygous males are cryptorchid.
Thus cryptorchidism is thought to be a sex-limited autosomal recessive
What breeds are affected by cryptorchidism?
This is a fairly common condition, which is seen most often in the
toy and miniature poodle, pomeranian, Yorkshire and Cairn terrier,
dachshund, Chihuahua, Maltese, boxer, Pekingese, English bulldog,
miniature schnauzer, and Shetland sheepdog.
For many breeds and many disorders, the studies to determine the mode
of inheritance or the frequency in the breed have not been carried out,
or are inconclusive. We have listed breeds for which there is a
consensus among those investigating in this field and among veterinary
practitioners, that the condition is significant in this breed.
What does cryptorchidism mean to your dog & you?
Dogs that are cryptorchid have a much increased risk of testicular
cancer (approximately 10 times). Castration will of course eliminate
Dogs with cryptorchidism can not be shown.
How is cryptorchidism diagnosed?
Your veterinarian will diagnose this condition when s/he examines
your dog at the time of vaccination. Most affected dogs have 1 testicle
that is not descended.
How is cryptorchidism treated?
The only treatment for this condition is removal of both testicles
(neutering or castration). Dogs with cryptorchidism should be castrated
for 2 reasons: if the testicles are not removed, there is an increased
risk of testicular cancer, and if your dog is bred, the trait will be
passed on to future generations.
Affected dogs should be not be bred. It is best not to breed their
parents as well, who carry the gene.
INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.
Copyright © 1998 Canine
Inherited Disorders Database. All rights reserved.
Revised: December 05, 2001.
This database is a joint
initiative of the Sir James Dunn Animal Welfare Centre at the Atlantic
Veterinary College, University of Prince Edward Island, and the
Veterinary Medical Association.
Permission to reprint granted by
Alice Crook, DVM Coordinator, Sir James Dunn Animal Welfare Centre
Atlantic Veterinary College University of Prince Edward Island
DVM and Marty Smith, DVM
Drs. Foster & Smith, Inc.
At birth, the testicles of a puppy are still within its abdomen. As the
animal develops, the testicles slowly "descend" into the scrotum. In
mammals, sperm development does not occur correctly at the high
temperatures found within the body. The testicles are therefore held
outside of the abdomen and within the scrotum to provide a cooler
environment. The production of testosterone is usually not influenced
Frequently, owners notice that the puppy they just purchased only has
one or possibly no testicles within the scrotum. Although different
dates are listed in some of the veterinary literature, both testicles
are usually within the scrotum by the time the animal is six weeks of
and they should definitely be there by the time the puppy is eight to
weeks of age. If one or both testicles are not present at that location
twelve weeks of age, they probably never will be and the animal is said
be suffering from cryptorchidism or "retained testicles." This is a
disorder that may be passed from generation to generation.
What are the symptoms?
These animals rarely show any abnormalities because of this condition.
They have normal activity levels, growth and behaviour. Although
fertility may be affected, they will usually show normal breeding
behaviour and frequently impregnate females, especially when one of the
testicles has descended into the scrotum.
What are the risks?
Some researchers believe that dogs with cryptorchidism may have a
higher incidence of other testicular diseases. Specifically, these
would be cancer and torsion.
What is the management?
Cryptorchid dogs should never be allowed to breed. This is a well
documented genetic trait, passed on to future generations. In addition,
because of the potential for an increased incidence of torsion or
cancer within the retained testicle, it is strongly recommended that
all of these individuals be neutered. The surgery to remove a retained
testicle is more involved than a routine neuter. The veterinarian must
literally hunt for the testicle which may be located anywhere from the
area around the kidney in the abdomen to the muscle near the groin.
back to top
by D. Caroline Coile, Ph.D.
Human parents may rejoice at
counting 10 fingers and 10 toes, but dog breeders need only count to
two to be grateful: two testicles, that is.
First appeared in Dog World magazine
At birth a male puppy's testicles are still within the abdomen, but
they slowly descend into the scrotum by about 10 days after birth. They
may be hard to locate at first, but by 6 to 10 weeks they should be
easily located in the scrotum. If not, there is only a small chance
they will descend. However, they are soft and can still move between
the scrotum and inguinal canal,
especially when the pup is cold or scared, so they may appear to come
go until the pup's inguinal rings close at about 6 months of age. At
time, a dog with only one descended testicle is termed a unilateral
and one with no descended testicles is a bilateral cryptorchid.
The reported incidence of cryptorchidism in dogs ranges from 1 to 10%,
with many more almost certainly unreported. Unilateral cryptorchids
occur more often than bilateral, and the retained testicle is usually
the one on
the dog's right side. Cryptorchidism is reported most often in Toy
Poodles, Pomeranians, Yorkshire Terriers, Miniature Dachshunds, Cairn
Terriers, Chihuahuas, Maltese, Boxers, Pekingese, English Bulldogs, and
small or short-nosed breeds in general. In humans, about 3-6% of
newborn males are cryptorchid, rising to 9-30% in premature males. Low
birth weight, being one of a twin, and maternal
exposure to estrogen during the first trimester all predispose a human
Hereditary factors are assumed to play an important role even in
humans, where 7% of brothers of cryptorchids are also cryptorchids.
Certain inbred families of dogs, notably Cocker Spaniels and Miniature
Schnauzers, have increased rates of cryptorchidism. Some of the most
telling data come from selective breeding in goats. Deliberate use of
cryptorchid sires raised the incidence in a goat herd from 7% to 51%;
then subsequently in that same herd strict selection against
cryptorchids (using only entire sires, and using neither a parent of a
cryptorchid nor offspring of a known carrier) decreased the incidence
The genetics aren't known, although it's commonly speculated that the
trait is a sex-limited (that is, can only be seen in males) autosomal
(non-sex chromosome) recessive (takes two) trait, meaning that both
males and females can be carriers. That means that if a breeder
seriously wants to rid the trait
from a line, then not only affected males, but sisters, mothers, and
of affected males must be pulled from the breeding pool. This would
such a devastating blow to most gene pools that it's not reasonable.
possibility is that cryptorchidism is a polygenic trait, that is,
from the interplay of multiple genes. This would make it even more
Cryptorchid dogs can't be shown in conformation, and bilaterally
cryptorchid dogs are sterile. A retained testicle is about 10 times
more likely to become cancerous, and its spermatic cord is also more
likely to become twisted causing testicular torsion, but the chances of
both are still fairly low. Nonetheless, because of these potential
problems a retained testicle should usually be surgically removed.
Breeders hoping to avoid these problems often turn to veterinarians for
help in encouraging a reluctant testicle. In humans, surgical
is the treatment of choice. The same procedure is possible in dogs, but
because such treatment is considered a fraudulent change of appearance
by the AKC, and because such dogs could then be used at stud and
perpetuate the trait, veterinarians consider it unethical.
Drug therapies are often tried. Much controversy exists over whether
such treatment is effective because few if any studies include control
cases. Repeated doses of drugs such as human chorionic gonadotropin
(HCG) or gonadatropin releasing hormone (GnRH) are given to stimulate
androgen production, which in turn appears to influence testicular
descent by affecting the testicular cord or cremaster muscle. In
humans, no difference in efficacy has been found between 4 doses
compared to 10 doses of HCG; nonetheless, it is commonly given twice a
week for five weeks. Success rates in humans range from 6-21 % in
randomized blind studies, and much higher in uncontrolled studies.
GnRH may give better results, and is available as a nasal spray instead
of injection, but is only improved for treatment of cryptorchidism in
humans in Europe. Success rates in controlled human studies range from
6-38%, and in uncontrolled studies from 13-78%. In a comparison of HCG
and GnRH, the HCG had a success rate of 6% and the GnRH 19%. Some
investigators advocate using both therapies.
These percentages only apply for humans. Little hard data is available
for dogs, but one study in which HCG was given four times over a
two-week period reported success in 21 out of 25 dogs, with better
results when given to puppies less than 16 weeks old.
Some veterinarians and breeders consider even drug therapy unethical.
However, side effects are minimal, and if medical treatment can reduce
need for abdominal surgery in a hunt for retained testicles, it would
unethical not to try it. Retained testicles predispose dogs to some
problems, but in many breeds the most serious threat it poses is
The sad truth is that dogs in breeds in which pet homes are seldom
may be euthanized because they cannot be used for show. And while
such dogs may raise the probability of producing more cryptorchids, the
condition is not as devastating as many other conditions dogs are
routinely bred with.
Until the time a DNA test becomes more available, and the mode of
inheritance and other possible factors are better understood, breeders
will continue to make their best bet and then hold their breath and
count to two.
The above information is simply
informational. It's intent is not to replace the advice of a
veterinarian nor to assist you in making a diagnosis of your pet.
Please consult with your own veterinarian for confirmation of any
diagnosis. Your pets life may depend on it