Some people have a testicle on only one side. On the other side, the testicle is completely missing or it may be felt as a lump in the groin. In either case, it is called ‘undescended testicle’.

How Undescended Testicle Occurs

Your testicles started to develop when you were a tiny foetus (a few weeks after you were conceived). They began high inside your abdomen, near the kidneys at the back. About 6 months before you were born, they started to journey forwards and downwards towards the groin. Meanwhile, your scrotum was developing ready to receive them. About a month or two before birth, the testicles normally complete the journey by descending into the scrotum.

In 2–4% of boys, one testicle doesn’t make the journey from the back of the abdomen to the scrotum before birth. Instead, it becomes stuck inside the abdomen or at the groin. This is why it is called ‘undescended testicle’. No one knows why it happens. It is more common in premature babies.

Most babies with undescended testicle do not need any treatment – in 2 out of 3 cases the testicle will come down naturally before the baby is 3 months old. If not, the baby will usually need an operation to bring the testicle down. This should be done between 6 and 12 months of age (Seminars in Pediatric Surgery 2010;19:215–224).

What to Do If You Have Only One Testicle

If you are a teenager or an adult with an undescended testicle you should definitely see your doctor. Your doctor should refer you to a hospital specialist (urologist). There is no need to feel embarrassed, because all doctors know this is a problem that needs attention. There are at least several issues that you will need to discuss with the urologist.

Testicular cancer. An undescended testicle is slightly more likely to develop cancer than a normal testicle. The risk is roughly 1 in 2,000. (The risk of testicular cancer in all men is about 1 in 100,000.) In fact, cancer of the testicle is almost always curable, partly because men easily notice a lump on their testicle and therefore it is caught at an early stage. But if the cancer develops in a testicle that is hidden up in the abdomen, it will be difficult to detect. A testicle that has become stuck in the abdomen is unlikely to be producing sperm, so the urologist may suggest that you have an operation to remove it, to prevent it becoming cancerous in the future. This is a complicated decision, which you will have to discuss in detail with the urologist. It may depend partly on your age; cancer of the testicle is most common in young men, so after the age of about 32 years the risk of the operation may outweigh the likelihood of getting cancer and it might be better to do nothing, but your urologist will advise you.

Fertility. If you have only one testicle you may be worrying about fertility. Although the undescended testicle probably isn’t doing much, you need not be too worried because your other normal testicle is likely to be producing many millions of sperms.

Torsion. An undescended testicle is not firmly anchored, and can become twisted on the tissues that surround it. This is called ‘torsion’. Episodes of torsion are very painful. So if you have abdominal pain as well as an undescended testicle stuck in the abdomen, your doctor will need to consider the possibility of torsion.

Testicular implants. If having an empty scrotum on one side bothers you, you can ask the urologist about having an artificial implant to give the appearance and feel of a normal testicle. These are either silicone, or a silicone bag filled with saline (similar to a breast implant).


First published on:
Reviewed and edited by: Matt Brewer
Last updated: May 2021

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