A child's testicles develop before birth. They start inside the abdomen. The testicles should then move down into the scrotum just before birth. Undescended testes stay in or return to the abdomen. A true undescended testicles situation is present at birth. The testicle remains in the abdomen until treated. Other situations that allow the testicles to go up into the abdomen include:

  • Retractile testicles—the testicles can move freely between the scrotum and abdomen. This condition does not require treatment and usually disappears by puberty.
  • Ascending testicles—a normal testicle returns to the abdomen

Undescended Testis
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Undescended testicles are often caused by a disruption in the development of the testicles. The cause of this disruption is not clear. Genetics may play a role. There may also be some problems with the hormones that help testes develop. The testicles may also have been injured at some point during the pregnancy.