Undescended testes and retractile testes

[Dave Paprocki]

Undescended testes (cryptorchidism) are testes that remain in the abdomen or the groin instead of descending into the scrotum. Retractile testes (hypermobile testes) have descended into the scrotum but can move back (retract) into the inguinal canal easily as a reflex response to stimulation.
In the fetus, the testes (testicles) develop within the abdomen. After the testes develop, but typically before birth (usually in the last third of pregnancy—the third trimester), they descend through a tunnel from the abdomen into the groin (the inguinal canal) and then down into the scrotum.
After the testes descend, the tunnel usually closes. If the tunnel does not close completely, an inguinal hernia may develop. The inguinal hernia rarely causes symptoms, but doctors can often feel it.
Sometimes, fluid from the abdomen accumulates around the testes and is trapped in the scrotum after the tunnel closes. This trapped fluid forms a soft lump called a hydrocele, which usually goes away in the first year of life. (See also Scrotal Swelling.)