Also known as cryptorchidism, undescended testes is a congenital condition characterized by testicles that do not extend to the scrotum.

In the fetus, the testes are in the abdomen. As development progresses, they migrate downward through the groin and into the scrotum. This event takes place late in fetal development, during the eighth month of gestation. Thirty percent of premature boys have testes that have not yet made the full descent. Only 3-4% of fullterm baby boys have undescended testes, and half of those complete the journey by the age of three months. Eighty percent of all undescended testes cases naturally correct themselves during the first year of life. Undescended testes that are not corrected can lead to sterility and an increased risk of testicular cancer.

The cause of undescended testes is presently unknown; however its symptoms are quite apparent. One or both of the testicles can be undescended, making the testicles appear missing or lopsided.

One form of diagnosis is the newborn examination, in which the doctor always checks for testes in the scrotum. If they are not found, a search will be conducted, but not necessarily right away. In most cases, the testes will drop into place later. If the testes are present at all, they can be anywhere within a couple inches of the appropriate spot. In 5% of cases, one testis is completely absent. In 10%, the condition occurs on both sides. Presence of undescended testes is indicated by measuring the amount of gonadotropin hormone in the blood.

Once doctors determined that the testes will not naturally descend, surgery becomes necessary. The procedure is called an orchiopexy and is relatively simple once the testes are located. The surgery is usually performed when the boy is between one to two years old.

Undescended testes must be treated to eliminate the increased risk of testicular cancer and the possibility of sterility. Undescended testes are twice as likely to develop cancer. Ten percent of all testicular cancers are in undescended testes.