During fetal life, the testes usually migrate from their original position near the kidneys towards their final position in the scrotum by the time a boy is born.
In some boys, this migration has not occurred or has only partially occurred, so that the testes are still inside the body at birth. This condition is called “undescended testes” or, in medical terms, cryptorchidism (pronounced kript-OR-kuh-dism) In some cases, both of the testes fail to descend (bilateral cryptorchidism), but in others, just one testis may remain undescended (unilateral cryptorchidism).
Testicular descent relies on hormonal signals (mostly involving the hormones INSL3 and testosterone).
Cryptorchidism usually can be attributed to gene defects that:
Because testicular descent depends on hormone action, there is growing evidence that cryptorchidism can also result from exposure of pregnant mothers to so-called endocrine-disrupting compounds (EDCs) - chemicals present in the environment that interfere with hormone action. EDCs have been associated with some plastics, fertilizers, pesticides, cosmetics, cookware coatings, fabric treatments, and many other chemicals that feature in daily life. The use of these chemicals has increased dramatically over the last 50 years.
Perhaps because there are so many components in the cascade of hormonal signals required for testicular descent, cryptorchidism is the most common birth defect of the male genitals, affecting about 3% of full-term and 30% of premature baby boys. This condition often corrects itself within a few months of birth, making the incidence of persistent cryptorchidism around 1%.
One-third of cases are bilateral, two-thirds unilateral.
About 80% of cryptorchid testes descend by the first year of life (the majority within three months). Persistent undescended testes are associated with reduced fertility, increased risk of testicular germ cell cancers and psychological (self-image) problems as the boy grows up.
Undescended testes may be an indicator of a broader developmental issue, or be part of a genetic syndrome, and so might warrant further medical tests.
For infant boys, a pediatrician is usually able to determine by feel whether one or both undescended testes are close to the exit from the body cavity, in which case descent within the first year is likely. If the testis or testes can’t be felt (that is, are not “palpable”), then ultrasound or magnetic resonance imaging (MRI) can determine whether any testes are present at all, where they are, and whether or not other internal structures are typical for male development. Analysis of the child’s sex chromosomes (XX or XY) might also be undertaken in those cases.
Persistent undescended testes are usually moved into the scrotum by a surgical procedure called orchiopexy (pronounced OR-kee-o-pex-ee) usually before the age of two. If testes remain in the abdominal cavity, there is a risk of reduced fertility associated with elevated testis temperature, and a low (~1%) risk of testis cancer; there may also be self-esteem issues associated with an empty scrotum later in life.
Parents are advised to seek the services of a qualified medical practitioner when considering any diagnostic or treatment options. See Disclaimer.
Further reading
Kids Health Info: Undescended testes (http://www.rch.org.au/kidsinfo/fact_sheets/Undescended_testes/)
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Last updated: 6 August 2021 PK
Edit history: Author P. Koopman 9/2009; revised PK 5/2011, 3/2013, 5/2013, 8/2013, 7/2015