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Hydrocele in adults

A hydrocele is a collection of fluid in the scrotum. Most develop for no apparent reason, are harmless and can be left alone. If needed, a small operation can usually cure the problem. In a small number of cases, a hydrocele is due to an underlying problem with a testicle (testis).

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What is a hydrocele?

A hydrocele is a collection of fluid in a sac in your scrotum next to a testicle (testis). It usually occurs on one side but sometimes a hydrocele forms over both testicles (testes).

Diagram of a hydrocele


The normal testis is surrounded by a smooth protective tissue sac. You cannot normally feel this. It makes a small amount of 'lubricating' fluid to allow the testis to move freely. Excess fluid normally drains away into the veins in your scrotum. If the balance is altered between the amount of fluid that is made and the amount that is drained, some fluid accumulates as a hydrocele.

What do hydroceles look and feel like?

A hydrocele feels like a small fluid-filled balloon inside your scrotum. It feels smooth and is mainly in front of one of your testicles (testes).

Hydroceles vary greatly in size. Very large hydroceles are sometimes seen in elderly men who have never shown their swelling to a doctor. It might have been getting larger over a number of years.

Hydroceles are normally painless. Large hydroceles may cause discomfort because of their size. Walking or sexual activity may become uncomfortable if you have a very large hydrocele.

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The normal scrotum and testes

The scrotum is normally loose, soft and fleshy. It holds the two testicles (testes). Usually you can easily feel your testes in your scrotum. A tube (the vas deferens) takes sperm from each testicle (testis) to the penis. It is normal for one testis to hang lower than the other.

See the separate leaflet called The male reproductive system.

What causes hydroceles in adults?

Most hydroceles occur in adults and are most common in men aged over 40 years.

  • The cause is not known in most cases.

  • A small number of hydroceles are caused when something is wrong with one of the testicles (testes). For example, infection, inflammation, injury or tumours of your testicle (testis) may cause fluid to be formed which leads to a hydrocele forming.

  • Sometimes hydroceles develop when there is generalised swelling of the lower half of your body due to fluid retention.

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Are hydroceles common?

They are relatively uncommon. Around 1% of men will have a hydrocele.

How do they test for hydroceles?

A doctor will examine your testicles (testes). Your doctor may also shine a light through your scrotum, which helps to diagnose a hydrocele.

If the hydrocele is large, and the doctor cannot feel your testicle (testis), the fluid may be drained with a needle and syringe. (This is helped by injecting local anaesthetic into the overlying skin to make the procedure painless.) Once the fluid is removed, your testes can then be examined more easily.

Sometimes your clinician may ask you to have an ultrasound scan of your testes. This can check your testes to make sure there is no underlying cause for the hydrocele.

What are the treatments for hydrocele?

Leaving it alone is an option

In adults, if the hydrocele causes no symptoms, one option is simply to leave it alone. You can use a support to be more comfortable. If it becomes larger or troublesome, you can always change your mind and have treatment.


Surgery may be recommended if your hydrocele is large or uncomfortable. The operation for a hydrocele involves making a very small cut in the scrotum or abdominal wall (lower tummy). The fluid is then drained from around the testicle (testis). The passage between the abdomen and the scrotum will also be sealed off so the fluid cannot re-form in the future.

This is a minor operation and is performed as a day case, so does not usually involve an overnight stay in the hospital. A hydrocele may return after surgery but this is very uncommon.


The fluid can be drained easily with a needle and syringe. However, following this procedure, it is common for the sac of the hydrocele to refill with fluid within a few months. Draining every now and then may be suitable though, if you are not fit for surgery or if you do not want an operation.


Sclerotherapy is the injection of a solution to stop the hydrocele recurring after having it drained. This is not commonly undertaken but may be offered to some people who are not suitable to have an operation.

Are hydroceles dangerous?

Not usually. Complications that can occur from an untreated hydrocele in an adult man usually depend on the cause.

Further reading and references

Article history

The information on this page is written and peer reviewed by qualified clinicians.

  • Next review due: 25 Jul 2028
  • 27 Jul 2023 | Latest version

    Last updated by

    Dr Rachel Hudson, MRCGP

    Peer reviewed by

    Dr Caroline Wiggins, MRCGP
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