Testicles grow in a boy’s abdomen early in a boy’s development while in the womb. Before birth the testicles descend into the scrotum.

An undescended testicle occurs when a testicle remain in the abdomen, failing to drop and reach the normal position in the scrotum (the sac that sits under the penis and houses the testicles).

Around 3% of male babies are born with at least one undescended testicle. For premature babies it is more common at around 30%. In around 80% of these cases the testicle drops within the baby’s first year (the majority within three months).

In most cases there is no specific reason why the testicle doesn’t drop into the scrotum and it’s likely due to a “mechanical problem” in which the testicle is misplaced along its path to the scrotum. The body later corrects this in the first three months and the testicle drops. In some rare cases there could be a hormone issue or a physical issue.

Upon a physical examination a doctor can determine if a testicle in missing from the scrotum. Typically, the baby will be monitored by the parents and the doctor to see if the testicle drops on its own. In extreme cases an ultrasound or MRI (magnetic resonance imaging) will be used.

In the majority of cases the doctor will choose to wait to see if the testicle drops on its own. As mentioned previously this will happen in most baby boys.

If the testicle doesn’t drop within 6 months the doctor may choose to use an ultrasound or MRI to locate the testicle and determine if there is need for surgery to bring the testicle down. In extreme cases where a testicle is not found on an ultrasound or MRI, a doctor may choose to perform a laparoscopy in which a small cut is made in the abdomen in order to physically look for the testicle.

The surgical procedure required to bring the testicle down is called an orchiopexy and has a high rate of success.