Testis mal-descent

Occurs when the testis is arrested in some part of its normal path to the scrotum

• Differentiate from ectopic testis - abnormally placed outside this path

Incidence

• About 4% of boys have one or both incompletely descended at birth
• 2/3 of these reach the scrotum during first three months
• Full descent after first three months is uncommon
• Overall incidence of testicular mal-descent at 1 year is 1%

Pathology

• More common on the right
• Bilateral in 20% of cases
• May be:
  • Intra-abdominal (usually lying extraperitoneal, just inside the internal ring)
  • Intra-canalicular - may or may not be palpable
  • Extra-canalicular - scrotal neck
  • Ectopic - commonly superficial inguinal pouch (just inferior and medial to the superficial ring), femoral triangle, root of penis, or perineum
• Testis is usually macroscopically normal in early childhood but typically smaller by puberty than normal boys
• Microscopic changes apparent from 1-2 years of age (higher testis has higher degree of change)

Consequences

• Impaired fertility - paternity rates around 2/3 normal if unilateral and 1/3 normal if bilateral
• Malignancy - 5-10x greater cancer risk than normal, most commonly seminoma. Unclear whether early orchidopexy removes this risk.
• Hernia - patent processus vaginalis in 90%
• Testicular torsion - higher risk

Examination

• Key question is whether this is retractile or undescended - retractile testis can be gently milked down and require no treatment
• Need a relaxed boy in a warm room and supine position
• Check for scrotum development - in undescended testes, it should be underdeveloped, while in retractile testes, it is generally normal

Treatment

• Orchidopexy should be performed before the age of 12 months
• Performed through a short incision over the deep ring
• Mobilise the testis down to scrotum and secure in a pocket between dartos muscle and skin
• Ligate and divide processus vaginalis , coverings of spermatic cord and fibrous bands at level of internal ring
• Sometimes a two-stage procedure is necessary
• Consider orchidectomy if the testis is later found to be atrophic