Cryptorchidism

Cryptorchidism (undescended testis) is the failure of one or both testes to descend from the retroperitoneal space through the inguinal canal into the scrotum. Testicular descent occurs in two phases: transabdominal (weeks 10-15, guided by insulin-like factor 3/INSL3 from Leydig cells) and inguinoscrotal (weeks 25-35, dependent on androgens and the gubernaculum). The undescended testis is exposed to the higher core body temperature (37°C vs 33°C in scrotum), which impairs spermatogenesis (requires cooler temperature) and increases malignant transformation risk. Germ cell degeneration begins by age 6 months in undescended testes, and by 1-2 years, histological changes include decreased germ cells, Leydig cell hyperplasia, and delayed maturation. The risk of testicular cancer is 4-8x higher in undescended testes, with seminoma being the most common malignancy.

Diagnostics & workup: - Physical examination: palpate for testis along the inguinal canal, femoral triangle, and perineum; distinguish from retractile testis (can be manipulated into scrotum and stays temporarily -- normal cremasteric reflex, does NOT require surgery) - Bilateral nonpalpable testes: evaluate for disorders of sexual development (DSD) -- karyotype, serum electrolytes (salt-wasting CAH can present as phenotypic male with bilateral nonpalpable testes), 17-hydroxyprogesterone, testosterone, AMH, LH, FSH - HCG stimulation test: for bilateral nonpalpable testes, HCG injection should produce testosterone rise if functional testicular tissue exists; no response suggests anorchia (absent testes) - Müllerian inhibiting substance (AMH/MIS): elevated indicates functional testicular tissue is present somewhere (useful for bilateral nonpalpable testes) - Imaging: ultrasound has limited sensitivity for nonpalpable testes (poor at localizing intra-abdominal testes); MRI can help but is not definitive - Diagnostic laparoscopy: gold standard for locating nonpalpable testes and determining if viable testicular tissue is present intra-abdominally