Testicles are formed prior to birth in the abdomen below the kidneys, and progressively descend during pregnancy from the abdomen through the groin into the scrotum. An undescended testicle is a testis that fails to descend into the scrotum. The incidence of undescended testicles in the general population for a full-term baby boy is about 3 percent, while the incidence can be as high as 25 to 33 percent in a preterm or premature boy.
About half of the testicles that are initially in the groin may descend into the scrotum, usually within the first few months of life. If one or both of the testicles have not descended into a normal location in the scrotum by six months of age in a full term baby, the chances of the testis coming down on its own in the future is very low. Surgery is recommended by the age of one year if the testicle(s) are not in the scrotum by that time.
Generally, there are no symptoms in a boy with an undescended testis. However, on physical exam, the testicle would be felt someplace other than the scrotum or in some cases, may not be felt at all on examination.
A child’s primary care physician will examine the size and location of the testes at each well-child exam. Referral to a pediatric urologist for surgical management is appropriate when the testes have not descended by 6 months of age or if there is difficulty feeling the testes in the normal scrotal location at some point later in life.
The purpose of surgery for correction of undescended testes is to preserve the function of the testis and to make the exam of the scrotum easier for the patient and physician to check for any future abnormalities. This surgery (called an orchiopexy) is generally an outpatient procedure which is well-tolerated by the patient. Testicles that are located higher in the abdomen may require more extensive surgery or multiple procedures to allow the testis to be relocated to the scrotum.
Occasionally, an abnormal or nonfunctional testis is found during surgical exploration and this may require testis removal as opposed to relocation into the scrotum.
In young children, there can be an active muscle reflex of the muscle fibers connecting to the testis. This may cause some mobility in the location of an otherwise normal testis, mimicking an undescended testis. These retractile testes can be manipulated into the scrotum once the muscle reflex is fatigued. Truly retractile testes are a normal physiologic variant and do not require surgery, but should be monitored closely by the primary care physician as the child grows.
The testicle is most healthy when it resides in the scrotum because the body temperature there is slightly cooler than the rest of the body. Testicles that are undescended and not in the scrotum all of the time can undergo changes in their internal architecture over time, especially if they remain high and are not corrected prior to puberty. This can have an effect on male hormone production and fertility potential later in life.
Also, there is a slightly higher incidence of tumors of the testis later in life (after 30-40 years of age) in those with undescended testes and testes that are not in the scrotum are more challenging for the patient to self-examine or for the primary care provider to check on routine exam.