What are the possible causes of a testis that is not palpable in the scrotum but can be felt higher in the inguinal or pelvic region?

Differential Diagnosis: Testis Palpable in Inguinal/Pelvic Region but Not in Scrotum

The most likely diagnosis is cryptorchidism (undescended testis), which represents failure of normal testicular descent and occurs in 0.7-3% of male infants, with the testis arrested at various points along its normal descent pathway. 1, 2, 3

Primary Differential Diagnoses

Cryptorchidism (Undescended Testis)

• This is the most common cause when a testis is palpable in the inguinal canal or lower abdomen but absent from the scrotum 1, 2
• The testis fails to complete its normal three-phase descent: abdominal translocation, transinguinal migration, and inguinoscrotal migration 1
• Location distribution varies:
  • Inguinal location is most common in rabbits and horses, and occasionally found in humans 1
  • Abdominal location (high in pelvis/abdomen) occurs when transinguinal migration fails 1, 2
  • The testis may be palpable at the internal inguinal ring or anywhere along the inguinal canal 2, 4

Acquired Cryptorchidism (Ascending Testis)

• Affects 1-2% of boys and represents secondary ascent of a previously descended testis 2
• Results from failure of spermatic cord elongation to keep pace with body growth 2
• Typically presents at 5-10 years of age, later than congenital cryptorchidism 2
• The testis was previously in the scrotum but has "ascended" back into the inguinal region 2, 4

Retractile Testis (Not True Cryptorchidism)

• Many nonscrotal testes are actually retractile and require no therapy 5
• The testis can be manually manipulated into the scrotum and remains there temporarily without tension 5
• This is a normal variant caused by an overactive cremasteric reflex, not a pathologic condition 5
• Critical distinction: Must be excluded from cryptorchidism diagnosis to avoid unnecessary treatment 5

Ectopic Testis

• The testis has deviated from the normal descent pathway and lies outside the normal anatomical route 1, 2
• Can be located in superficial inguinal pouch, perineum, femoral region, or other aberrant locations 2
• Less common than true cryptorchidism 2

Diagnostic Approach

Clinical Examination Specifics

• Attempt manual manipulation to distinguish retractile from truly undescended testis - if the testis can be brought into the scrotum and remains there without tension, it is retractile 5
• Examine in warm environment with patient relaxed to minimize cremasteric reflex 5
• Palpate carefully along the inguinal canal from internal ring to external ring 4
• Check for contralateral testicular hypertrophy - suggests the palpable mass may be an atrophic remnant rather than viable testis 4

Imaging Recommendations

• Ultrasound is NOT routinely recommended for palpable undescended testis 4
• For nonpalpable testis in an older, overweight boy, ultrasound may be appropriate to aid localization 4
• For truly nonpalpable testis, diagnostic laparoscopy is the gold standard - approximately 50% are abdominal/high inguinal and 50% are atrophic 4
• The ACR guidelines focus on scrotal abnormalities rather than undescended testis evaluation 6

Clinical Significance and Management Implications

Timing Considerations

• Spontaneous descent occurs in up to 70% during the first 6 months of life 3
• After 6 months, spontaneous descent is unlikely 3
• Identifiable histologic alterations develop within 2 years if the testis remains undescended 5
• Current guidelines recommend treatment between 6-12 months of age to maximize fertility potential and possibly reduce cancer risk 2, 4, 3

Fertility and Malignancy Risk

• Fertility is impaired even with successful orchiopexy - reported at 75% for unilateral and 50% for bilateral cases 5
• Testicular cancer risk is increased in cryptorchid testes and even affects the contralateral descended testis 5
• Early orchidopexy (before 18 months) may reduce cancer risk and improve fertility outcomes 4, 5
• The neonatal gonocyte transformation to type A spermatogonium (crucial for fertility) occurs at 3-12 months and is blocked in undescended testis 2

Common Pitfalls to Avoid

• Do not confuse retractile testis with true cryptorchidism - retractile testes require no intervention and should be excluded from treatment protocols 5
• Do not delay treatment beyond 12-18 months waiting for spontaneous descent after 6 months of age - data do not support monitoring into adolescence 4, 5
• Do not rely on hormonal therapy as primary treatment - hCG is effective in only a small percentage and GnRH is no better than placebo in properly designed studies 5
• For nonpalpable testis, do not assume it is abdominal - 50% are atrophic remnants, typically in the scrotum 4