Cryptorchidism (undescended testicle)
Cryptorchidism is a condition in which either one or both testes (testicles) fails to descend fully into the scrotum. Normally, the testicles will descend before birth. In young puppies (under 6 months) the testicles can occasionally retract back into the groin, particularly if the pup is cold or excited. There should, however, be periods of time when both testicles are properly located.
Cryptorchidism presents itself in one of two forms: 1) unilateral cryptorchidism - normal descent of only one testicle, 2) bilateral cryptorchidism - retention of both testicles. Unilateral cryptorchid dogs are usually capable of breeding, whereas bilateral cryptorchids are sterile. It appears that cryptorchidism is polygenetic (involves multiple genes), and therefore elimination of this condition from a gene pool is difficult. This condition occurs more often in some breeds of dog (Saint Bernards and German Shepherd Dogs) than in others, but can and does occur in all dog breeds. Cryptorchidism achieves its highest levels of occurrence in heavily line-bred animals. In spite of the fact that bilateral cryptorchid dogs are sterile, both bilateral and unilateral cryptorcids should be neutered, to reduce the risk of possible future complications. Unilateral cryptorchids should never be used in a breeding program.
The term undescended testicle or cryptorchidism describes the condition in which one or both testicles are not within the scrotum and can't be brought into the scrotum with external manipulation. A testicle may be located anywhere along its normal path of descent or in an ectopic location. Cryptorchidism is distinct from the situation when the testicle is "retractile," meaning that it can be brought into the scrotum by external manipulation or is seen in the scrotum sometimes. Young boys often have a strong "cremasteric reflex," which pulls up the testicles with stress or cold.
An undescended testicle may reside in the inguinal canal (the groin), inside the abdominal cavity, or in an unusual and "ectopic" location, such as above the pubic bone. Approximately 80% of undescended testicles can be found within the inguinal canal. Sometimes, the testicle is absent on one or both sides. It can be difficult to distinguish this situation from cryptorchidism, particularly if a testicle is present but inside the abdomen and not apparent on physical examination or even with imaging studies. The diagnosis of cryptorchidism is usually made by a child's parents or pediatrician. If a testicle can be brought into the scrotum, even if it retracts again on release, the diagnosis of cryptorchidism has been excluded and the testicle would be expected to assume a normal scrotal position when the endogenous (produced within) male hormone level of the adult is reached.
In humans, the testis develops in the abdomen and descends into the lower portion of the scrotum during the third trimester. When the testis is not found in its normal anatomical location, it can either be palpable elsewhere or be nonpalpable. When palpated outside the scrotum, the testis may be cryptorchid, ectopic or retractile, while a nonpalpable testis may be cryptorchid, atrophic or absent. Cryptorchidism occurs when the testis fails to descend into its normal postnatal location and may be found in the abdomen, in the inguinal canal, or at the external ring (prescrotal).
Cryptorchidism is a common disorder. The incidence of cryptorchidism in premature male infants is 9.2~30%, and in full-term infants is 3.4~5.8%. In the majority of these patients (95% of premature and 75% of full term infants) the testis will descend spontaneously within the first year of life. In boys one year of age, the incidence of cryptorchidism is 0.8%, and remains constant through puberty and adulthood, ranging from 0.5% to 0.8%. In one third of patients, cryptorchidism occurs bilaterally. When unilateral, the right side is more often affected (right:left = 7:3). The most common location of the cryptorchid testis is the inguinal canal (72%), followed by prescrotal (20%) and abdominal (8%) locations. In the abdomen, the undescended testis may be located anywhere from the renal hilum to just inside of the internal ring.
The cryptorchid testis requires surgical correction, to avoid the complications associated with the undescended testis: the psychological impact of having abnormal external genitalia, infertility, malignant degeneration, torsion and bowel incarceration.
Because of the high incidence of complications, early treatment including hormonal therapy, orchiopexy and orchiectomy, is important. Gonadotropin-releasing hormone (GnRH) and human chorionic gonadotropin (hCG) are currently used for hormonal therapy. While these hormones are very successful in treating the retractile testis, their success rate is relatively low (6 18%) in the treatment of the truly undescended testis. Because of the possibility of spontaneous descent, surgical intervention is usually delayed until after one year of age. Orchiopexy is usually performed in patients between 1 and 10 years of age, and orchiectomy is considered in patients after puberty. It was previously observed that after 32 years of age, the surgical risk outweighed the risk of malignancy and thus, surgical intervention was not indicated in these patients. However , with modern anaesthetic techniques, the surgical risk is markedly reduced and thus, orchiectomy may still be warranted especially in older adults with abdominal testis.