Undescended and Retractile Testes
Undescended testes (cryptorchidism) are testes that remain in the abdomen instead of descending into the scrotum just before birth. About 3 of every 100 boys have undescended testes at birth. Most testes descend on their own within about 6 months. Boys born prematurely are much more likely to have the condition; so are boys whose family members had undescended testes. Half of the boys with the condition have an undescended testis only on the right, and one fourth are affected on both sides.
 See the figure Undescended Testis.
Undescended testes cause no symptoms. However, undescended testes can become twisted in the abdomen (testicular torsion (see Section 21, Chapter 238)), impair sperm production later in life, and increase the risk of hernia and testicular cancer. Surgery is generally performed to bring the testes down into the scrotum if the testes remain undescended at 1 year of age.
Retractile (hypermobile) testes are descended testes that easily move back and forth between the scrotum and the abdomen. Retractile testes do not lead to cancer or other complications. The testes usually stop retracting by puberty and do not require surgery or other treatment.
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