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What are Undescended Testicles (Cryptorchidism)?

What Happens under Normal Conditions?

How the testicles descend into the scrotum during pregnancy
How the testicles descend into the scrotum during pregnancy
Image © 2003 Fairman Studios, LLC.

The testicles (or "testes") are 2 organs that hang in a pouch-like skin sac (the scrotum) below the penis. The testicles are where sperm and testosterone (the male sex hormone) are made. The scrotum keeps the testicles in a cooler setting than the body. This is because sperm can't grow at body temperature. During childhood, sperm in the testicles go through a process that results in mature sperm at puberty.

Normal testicles form early in a baby boy's growth. They form in the lower belly (abdomen), but descend, or "drop," into the scrotum toward the end of pregnancy. Normal testicles attach themselves with stretchable tissue in the bottom of the scrotum. This is controlled by the baby's normal hormones.

What are Undescended Testicles?

An undescended testicle (or "testis") is when it fails to drop into the normal place in the scrotum. Your child's health care provider can find this during a routine exam. This issue is found in about 3 or 4 out of  100 newborns (and up to 21 out of 100 premature newborns). Luckily, about half of these testicles will drop on their own during the first 3 months of life. But testicles won't drop on their own after 3 months of age. Thus, about 1 or 2 out of 100 boys with undescended testicles will need treatment.

It's important not to confuse undescended testicles with "retractile" testicles. After 6 months of age, a male child has a reflex that temporarily pulls the testicles up to protect them when he's cold or frightened. These testicles are in the scrotum at other times and don't need treatment. Only testicles that are truly undescended need treatment. A pediatric urologist can tell the difference with a physical exam.

The testicles need to be 2 to 3 degrees cooler than normal body temperature to make sperm. The scrotum is many degrees cooler than body temperature, and so is the ideal place for the testicle. Testicles that don't drop into the scrotum won't work normally. The longer the testicles are too warm, the lower chances are that the sperm in that testicle will mature normally. This can be a cause of infertility, especially when both testicles are affected.

Undescended testicles are also linked to a higher risk of:

  • Testicular cancer in adulthood (though the risk is still less than 1 in 100)
  • Testicular torsion (twisting of the chord that brings blood to the scrotum)
  • Developing a hernia near the groin