Retained Testicle (Cryptorchidism) in Dogs
What is cryptorchidism?
Cryptorchidism is the medical term that refers to the failure of one or both testicles (testes) to descend into the scrotum.
If the testicles aren't in the scrotum, where are they?
In most cases of cryptorchidism, the testicle is retained in the abdomen or in the inguinal canal (the passage through the abdominal wall into the genital region through which a testicle normally descends). Sometimes the testicle will be located just under the skin (in the subcutaneous tissues) in the groin region, between the inguinal canal and the scrotum. In cases of abdominal cryptorchidism, the testicle cannot be felt from the outside. Abdominal ultrasound or radiographs may be performed to determine the exact location of the retained testicle. Many dogs will only have one retained testicle, and this is called unilateral cryptorchidism.
What causes cryptorchidism, and how common is it?
The testes develop near the kidneys within the abdomen and normally descend into the scrotum by two months of age. In certain dogs it may occur later, but rarely after six months of age. Cryptorchidism may be presumed to be present if the testicles can’t be felt in the scrotum after two to four months of age. Cryptorchidism occurs in all breeds, but the toy breeds, including toy Poodles, Pomeranians and Yorkshire Terriers, are at higher risk. Approximately seventy-five percent of the cases of cryptorchidism involve only one retained testicle while the remaining twenty-five percent involve failure of both testicles to descend into the scrotum. The right testicle is more than twice as likely to be retained as the left testicle. Cryptorchidism affects approximately 1.2% of all dogs. The condition appears to be inherited since it is commonly seen in families of dogs, although the exact cause is not fully understood.
What are the symptoms of cryptorchidism?
This condition is rarely associated with pain or other clinical signs (symptoms), until or unless a complication develops. In its early stages, a single retained testicle is significantly smaller than the other, normal testicle. If both testicles are retained, the dog may be infertile. The retained testicles continue to produce testosterone but generally fail to produce sperm. One complication of cryptorchidism is spermatic cord torsion (twisting onto itself). If this occurs, there will signs consistent with sudden and severe abdominal pain. More frequently, a cryptorchid or retained testicle will become cancerous. The clinical signs associated with testicular cancer depend upon the specific type of cancer.
Certain congenital abnormalities may occur with cryptorchidism. These include patellar luxation (dislocated kneecap), shortened or kinked tail, tetralogy of Fallot (a life-threatening heart defect), tarsal deformity (abnormal legs), microphthalmia (abnormally small eyes), and upper eyelid agenesis (eyelids that don’t develop).
What is the treatment for cryptorchidism?
Neutering and removal of the retained testicle(s) are recommended as soon as possible. If only one testicle is retained, the dog will have two incisions – one for extraction of each testicle. If both testicles are in the inguinal canal, there will also be two incisions. If both testicles are in the abdomen, a single abdominal incision will allow access to both.
What if I don't want to neuter my dog?
There are several good reasons for neutering a dog with cryptorchidism. The first is to remove the genetic defect from the breed line. Cryptorchid dogs should never be bred. Second, dogs with a retained testicle are more likely to develop a testicular tumor (cancer) in the retained testicle. Finally, dogs with a retained testicle typically develop the undesirable characteristics associated with intact males like urine marking and aggression.
"The risk of developing testicular neoplasia
is estimated to be at least ten times greater
in dogs with cryptorchidism than in normal dogs."
The risk of developing testicular cancer is estimated to be at least ten times greater in dogs with cryptorchidism than in normal dogs. Just over half of all Sertoli cell tumors and one third of all seminomas occur in retained testicles. Additionally, 36% of all spermatic cord torsions occur in dogs with cryptorchidism. A recent study concluded that a retained testicle, even if replaced in the scrotum surgically, had 13 times higher risk of developing cancer.
What is the prognosis for a dog with cryptorchidism?
The prognosis is excellent for dogs that undergo surgery early, before problems develops in the retained testicle. The surgery is relatively routine, and the outcomes are overwhelmingly positive.