Undescended testicles are a common childhood condition where a boy's testicles are not in their usual place in the scrotum.
It's estimated that about one in every 25 boys are born with undescended testicles.
In most cases, no treatment is necessary, as the testicles will usually move down into the scrotum naturally during the first three to six months of life. However, around one in 100 boys has testicles that stay undescended unless treated.
The medical term for having one or two undescended testicles is unilateral or bilateral cryptorchidism.
When to see your GP
Undescended testicles are usually detected during the newborn physical examination carried out soon after birth, or during a routine check-up at six to eight weeks.
See your GP if at any point you notice that one or both of your child's testicles are not in the normal place within the scrotum.
Undescended testicles aren't painful and your child isn't at risk of any immediate health problems, but they should be monitored by a doctor in case treatment is needed later on.
What causes undescended testicles?
During pregnancy, the testicles form inside a baby boy's abdomen (tummy), before slowly moving down into the scrotum about a month or two before birth.
It's not known exactly why some boys are born with undescended testicles. Most boys with the condition are otherwise completely healthy.
Being born prematurely (before the 37th week of pregnancy), having a low birth weight and having a family history of undescended testicles may increase the chances of a boy being born with undescended testicles.
Diagnosing undescended testicles
Undescended testicles can usually be diagnosed after a physical examination. This will determine whether the testicles can be felt near the scrotum (palpable) or if they can't be felt at all (impalpable).
This physical examination can sometimes be difficult, so your doctor may need to refer your child to a paediatric surgeon.
No further scans or tests are needed to locate the testicles if they can be felt by the doctor. If they cannot be felt, part of the initial surgical treatment (see below) may involve keyhole surgery (a diagnostic laparoscopy) to see if the testicles are inside the abdomen.
How undescended testicles are treated
If the testicles haven't descended by six months, they're very unlikely to do so and treatment will usually be recommended.
This is because boys with untreated undescended testicles can have fertility problems in later life and an increased risk of developing testicular cancer.
Treatment will usually involve an operation called an orchidopexy to move the testicle(s) into the correct position inside the scrotum. This is a relatively straightforward operation, with a good success rate.
Surgery is ideally carried out before 12 months of age. If undescended testicles are treated at an early age, the risk of fertility problems and testicular cancer can be reduced.
Read more about treating undescended testicles.