At what age should testicles be fully descended?

When Should Testicles Be Descended By?

Testicles should be fully descended by 6 months of age (corrected for gestational age), and if they remain undescended after this point, spontaneous descent is unlikely and surgical referral is mandatory. 1

Normal Testicular Descent Timeline

The physiologic process of testicular descent occurs in two distinct phases during fetal development:

• Transabdominal phase occurs during the first trimester (8-15 weeks of gestation), controlled by gubernacular enlargement and cranial ligament regression 2
• Inguinoscrotal phase occurs between 25-30 weeks of gestation and is androgen-dependent 1, 2
• At 22-25 weeks gestational age, testes are positioned at the internal ring 1
• Normal descent into the scrotum is completed between 25-30 weeks of gestational age 1

Prevalence at Birth and Spontaneous Descent

The likelihood of undescended testes at birth varies dramatically with gestational age and birth weight:

• 1-3% of full-term male infants have undescended testes at birth 1
• 15-30% of premature infants have undescended testes at birth 1
• Nearly 100% of extremely low birth weight infants (<900g) have undescended testes 1

Critical window for spontaneous descent:

• Spontaneous descent may occur during the first 6 months of life 1, 3
• After 6 months (corrected for gestational age), spontaneous descent is highly unlikely and will not occur 1
• The incidence dramatically decreases during the first 3 months after birth 3

When to Refer for Surgical Intervention

Referral to a surgical specialist should occur by 6 months of age (corrected for gestational age) if testes remain undescended. 1 This timing is critical because:

• The low probability of spontaneous descent after 6 months 1
• Continued damage occurs to testes remaining in non-scrotal locations 1
• Germ cell preservation requires early intervention 4

Optimal Surgical Timing

Orchidopexy should be performed between 6-18 months of age, with 18 months being the absolute latest recommended time. 4, 1

Evidence Supporting This Timeline:

Fertility preservation:

• The majority of cryptorchid boys have normal germ cell counts during the first 6 months of life 4
• After 15-18 months of age, some cryptorchid boys begin to lack germ cells in the testes 4, 1
• By 8-11 years of age, approximately 40% of bilateral cryptorchid boys have no germ cells in testicular biopsies 4, 1

Cancer risk reduction:

• Prepubertal orchidopexy results in a two- to six-fold reduction in relative risk of testicular cancer compared with postpubertal orchidopexy 4, 1
• The overall relative risk of malignancy in cryptorchid testes is 2.75-8 fold 4

Surgical success:

• Open surgical intervention success rates exceed 96% (range 89-100%) 4, 1
• Subsequent testicular atrophy occurs in less than 2% of cases 4, 1

Special Clinical Scenarios

Bilateral Nonpalpable Testes in Newborns

This is a medical emergency requiring immediate specialist consultation to evaluate for possible disorders of sex development, including congenital adrenal hyperplasia, which can be life-threatening. 1

Retractile Testes

Boys with retractile testes require annual monitoring, as 2-45% may develop secondary testicular ascent due to hyperactive cremasteric reflex, foreshortened patent processus vaginalis, or entrapping adhesions. 4

Acquired Cryptorchidism

Approximately 1-2% of boys develop acquired cryptorchidism (ascending testes) later in childhood, with peak prevalence around 8 years of age, due to failure of spermatic cord elongation with growth. 1, 2, 5 These cases typically present for surgery at 5-10 years of age 2, and some evidence suggests spontaneous descent may occur at puberty in select cases 6.

Common Pitfalls to Avoid

• Delaying referral beyond 6 months of age is the most critical error 1
• Ordering unnecessary imaging studies (ultrasound or other modalities) prior to specialist referral, which delays appropriate care 1
• Using hormonal therapy (hCG or GnRH) to induce descent, which has low response rates (6-38% in controlled studies) and lacks long-term efficacy 4, 3
• Failing to monitor retractile testes annually for secondary ascent 4
• Assuming older age at surgery is acceptable - while there may be some fertility benefits even with prepubertal orchidopexy performed after 18 months, progressive histologic damage continues 4