Cryptorchidism: The Undescended Testicle

Cryptorchidism is the technical term for an undescended testicle.  Undescended testes are the most common congenital abnormality of the male genitals occurring in approximately 1 in 600 live births.  Most undescended testes will descend spontaneously, so the incidence is about 1% full-term infants at one year.  However, up to 1/3rd of premature boys will have one or more undescended testes.

This blog will review the proposed mechanisms of cryptorchidism and treatment options.

Embryology and Etiology

During development of the male embryo, the primitive testicles form near the developing kidneys.  As the embryo grows, the testicles remain relatively still while the embryo grows and lengthens.  Under the influence of testosterone and other hormones, the testicles exit the abdominal cavity and settle in the scrotum at about the 8th month of pregnancy - explaining why the incidence of cryptorchidism is much higher in premature infants.

There are a number of theories to explain why testicles fail to descend.  There are some known genetic causes and approximately 14% of boys with cryptorchidism have a positive family history.  Additional support for genetic causes of cryptorchidism include a number of mouse models with culprit genes and the observation that infants with severe congenital syndromes, like congenital adrenal hyperplasia, Klinefelter's disease, autosomal trisomy or disorders of sexual differentiation, will often have cryptorchidism. Maternal obesity is associated with an increased risk of cryptorchidism, as is low birth weight and cesarean section delivery.  Finally, environmental exposure to "endocrine disruptors" that elevate estrogens or decrease androgens may affect the ultimate descent of the testicle.

Locations of undescended testicles.

Undescended testicles are usually found along the path of normal descent.  The path of descent can be halted in the abdomen, inguinal canal or high in the scrotum.

Intra-abdominal testicle.

Less commonly, testicles can be found in ectopic locations - the most common ectopic location is in the superficial inguinal pouch of Denis Browne.

Retractile Testis

Retractile testes are occasionally misdiagnosed for cryptorchidism.  Retractile testes are normally descended testicles that ascend or retract into the inguinal region due to a strong cremasteric reflex.  The cremaster muscle is the muscle of the spermatic cord that can pull the testicle upward when the inner thigh is stroked. The management for retractile testis is observation as approximately 30% will descend, 40% will remain retractile (but not have any problems), and 30% will ascend and require intervention.

Management of Cryptorchidism

There are a number of goals in the management of undescended testicles:

1. Preserve fertility
2. Prevent and monitor for testis cancer
3. Repair inguinal hernia
4. Reduce the risk of testicular torsion

Sperm form from germ cells in testicle.  Germ cells function ideally at 2 degrees cooler than normal body temperature - which is why they settle outside of the body in the scrotum.  If the testicles fail to descend, the germ cells will deteriorate at about 18 months.  The rates of infertility for men with cryporchidism is 10-13%.  

Cryptorchidism is the number one risk factor for testicular cancer.  (See our prior blog on The Basics of Testis Cancer Diagnosis: Epidemiology & Presentation for more details)  Boys and men with cryptorchidism have a higher risk than the general population for developing testis cancer in both the undescended testicle and the normal, undescended testicle. In addition, surgically lowering a testicle reduces (but does not erase) the risk of testis cancer.  In addition, lowering the testicle facilitates surveillance.

Both inguinal hernia and testicular torsion are more common in boys with undescended testis.  Upwards of 90% of boys with undescended testicles and 50% of ectopic testicles will have an associated, congenital inguinal hernia.  In addition, acute testicular torsion is more common in these boys and the salvage rate is much lower (<10%) than the general population.

Non-Surgical Management

Human chorionic gonadotropin (HCG) increases testosterone production by the testis.  In approximately 25% of patients, the testicle will descend.  Success rates are higher for lower testicles and works best for patients with testicles in the high scrotum or low inguinal canal.  However, approximately 15% of the successfully treated testicles will "re-ascend."  HCG should not be given to newborns or post-pubertal males.  Side effects include temporary masculinization and premature closure of epiphyseal plates and growth arrest.

Surgical Management

Surgery is the gold standard for the treatment of cryptorchidism.  Surgery is typically deferred to 1 year of age, given that most undescended testicles will descend by one year of age.  For boys with ectopic or high undescended testicles (who have a low likelihood of spontaneous descent), surgery can be done at six months or later when the risks of anesthesia are improved.  

The most common surgery for a palpable, undescended testicle is called orchiopexy.  The goal of orchiopexy is to lengthen the spermatic cord so that the testicle can  be brought down to the scrotum without tension on the vascular blood supply to the testicle.  With good fixation techniques (using a subdartos pouch and stay suture or pledgit), the success rate for orchiopexy is 89%.

For patients with non-palpable testicles, the initial step in management is to locate the testicle.  This is usually achieved with diagnostic laparoscopy - placing a camera in the abdomen to look for an intra-abdominal testicle.  Most commonly, a viable intra-abdominal testis is found (37%), spermatic vessels are found entering the inguinal canal (40%) or a "peeping" testicle is found at the inguinal ring (11%).  If a testicle is found or supsected of being present, attempts should be made to place it in the scrotum.  If an intra-abdominal testis is found, a variety of procedures can be performed to lower the testicle.  The success rates for correcting an intra-abdominal testis are lower than an inguinal orchiopexy and vary from 67-77%.  If spermatic vessels are found but no testicle is seen, efforts should then be made to locate the testicle in the inguinal canal, perform an inguinal exploration and orchiopexy if possible.  Less commonly, blind-ending spermatic vessels are found (10%) indicating that the testicle never developed or lost its blood supply early in development.  

The major complication for orchiopexy is testicular atrophy, which is caused by damage to the testicular blood supply.  

For more information on cryptorchidism, visit Pediatric Urology at the Children's Center at Johns Hopkins.