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During fetal development, the male's testicles form in the abdomen. In the final months before birth, the testicles move down into the scrotum — a small bag of skin underneath the penis. However, sometimes a testicle doesn't stay in its proper position in the scrotum, but glides back and forth between the scrotum and the groin — a condition called retractile testicle.

About 1 percent of preadolescent boys have a retractile testicle. Most often a retractile testicle descends on its own without treatment as a boy ages. Although a retractile testicle doesn't affect sexual development, it may reduce future fertility. A retractile testicle can also cause other complications and increase the risk of testicular cancer. For this reason, a doctor may surgically affix the retractile testicle to its proper position if it doesn't descend on its own.

A retractile testicle usually causes no noticeable symptoms. Like a yo-yo, the testicle glides in and out of the scrotum and groin — usually without pain or discomfort. A retractile testicle may:

• Move on its own or be moved by hand
• Move quickly or slowly
• Remain in the scrotum for a period of time before retracting again

A retractile testicle is different from an undescended testicle (cryptorchidism), which is fixed in place in the groin. An undescended testicle doesn't move on its own and can't be repositioned by hand.

Possible causes of a retractile testicle may include:

• Abnormal development of the fetal sex organs. During male fetal development, the testicles descend into the scrotum through a passageway or canal in the groin. Normally the canal then closes. Sometimes, however, a part of the canal remains open, leaving a potential escape route allowing the testicles to move back up into the groin.
• Tight spermatic cord. The spermatic cord houses blood vessels, nerves, the tube that carries semen and sperm from the testicles to the penis (vas deferens), and the small muscles that cause the testicles to retract (called the cremasteric muscles). The spermatic cord is normally very elastic. If it is abnormally tight or inelastic, it may pull the testicle out of the scrotum and up into the groin.

Certain factors may increase the risk of a retractile testicle, including:

• Previous testicle infection. Common testicular infections, such as epididymitis and orchitis, can leave scar tissue in and around the testicles. This scar tissue may adhere to normal groin tissue, pulling the testicle up and out of the scrotum.
• Groin injury. Trauma to the testicles or groin area may cause scar tissue to form and lead to retractile testicle.
• Hernia in the groin (inguinal hernia). An inguinal hernia can extend from the groin into the scrotum, interfering with the normal position of a testicle. Scarring from surgery to repair an inguinal hernia also can contribute to a retractile testicle.
• Premature birth. A boy born prematurely may have underdeveloped sex organs. As he grows, a testicle may be abnormally positioned.

If you have concerns about how your child's testicles are developing, check with your doctor. In most cases, your doctor will suggest watching and waiting as the boy matures. Seek medical care for your child if, after puberty, the testicle has not descended permanently on its own, or if the testicle permanently retracts (undescended testicle). Also, watch for signs that your son is hiding the condition. Signs that your son may be uncomfortable with his condition may be seen as refusing to participate in regular activities that require undressing and showering among other kids — like sports at school or swimming.

If your child has groin pain or swelling of the testicles or scrotum, see his doctor promptly.

If your son has a retractile testicle, your doctor should easily be able to move the testicle from the groin down into the scrotum during a physical examination. If the testicle can't be moved, or if it retracts immediately, your child may have an undescended testicle rather than a retractile testicle.

After diagnosis, your doctor will want to examine your child annually until his testicle naturally descends into the scrotum or has been surgically repositioned. Then long-term monitoring into adulthood is recommended to make sure the testicle doesn't retract again or cause complications.

Complications of a retractile testicle may include:

• Undescended testicle. In approximately 30 percent to 50 percent of boys with a retractile testicle, the testicle permanently retracts up into the groin, referred to as an acquired undescended testicle. If your child's testicle hasn't descended by age 7, the risk that it will become undescended is higher.
• Impaired blood flow to the testicle. As a retractile testicle moves, the spermatic cord can become twisted cutting off blood flow to the testicle, especially if the spermatic cord is tight. This condition, called testicular torsion, is extremely painful and requires prompt treatment. Untreated testicular torsion can destroy the testicle, increasing the chance of infertility.
• Infertility. A retractile testicle that becomes permanently retracted (an undescended testicle) and remains untreated may affect a boy's future fertility. However, a male with only one healthy testicle can still produce enough sperm to conceive a child. The risk of infertility usually decreases if the testicle is naturally or surgically returns to the scrotum.
• Testicular cancer. Abnormal changes in testicular tissue may result in the growth of a tumor. The risk of a testicular tumor is 35 times greater in males with an undescended testicle — a testicle that remains in the groin instead of moving down into the scrotum. And a retractile testicle has up to a 50 percent chance of becoming undescended. The risk of cancer remains even if the testicle has permanently descended on its own or has been moved into the scrotum surgically.

Most complications of a retractile testicle are reversed or decreased if the testicle descends permanently on its own or is moved into the scrotum surgically.

A retractile testicle usually will descend on its own without treatment. For this reason, watchful waiting usually is recommended for a retractile testicle. During watchful waiting, medications and surgery aren't used.

If a retractile testicle hasn't descended on its own by age 14, treatment options may include:

• Surgery. Surgery to relocate the testicle (orchiopexy) is the traditional treatment for a retractile testicle that doesn't descend on its own. This procedure involves a small groin incision through which the testicle is repositioned.
• Hormone therapy. Injections of a hormone called human chorionic gonadotropin (HCG) may stimulate a retractile testicle to move down into the scrotum. This hormone works by increasing the testicle's weight, causing it to drop into position in the scrotum.

Regularly check the position of your younger boy's testicles and keep a record of any changes. When he's older, your child can check his own testicles and let you know if he finds any changes.

In addition, your doctor should check your child's testicles once a year. Even if the testicle descends on its own or has been treated surgically, it's important to monitor it throughout life to make sure it stays in place and other complications don't develop.

A retractile testicle may be embarrassing for a young boy. But as your son matures, his scrotum will become more pendulous and normal looking. Reassure your child that as he ages his body will develop and change as well.

To help your young boy cope with a retractile testicle, suggest ways for him to conceal his groin when changing clothes in front of peers or sharing shower facilities at school. For example, he could wear loose fitting underwear, such as boxers instead of briefs. He also could choose to change early for gym class or wait to shower last afterward.

Explain why it's important for him to be aware of his condition and to tell you about any changes he notices. With sensitivity and patience, you and your doctor can help your child through this often worrisome time.