Testicular lumps and swellings - Causes 

  • Overview

Causes of testicular lumps and swellings  

There are many different causes of testicular lumps and swellings. 

Testicular cancer is a possible cause. About 2,000 cases of testicular cancer are diagnosed in the UK every year. However, less than four in 100 lumps are testicular cancer.

The main types of lumps and their causes are explained below.


The exact cause of varicoceles is unknown. However, most experts believe they are caused by abnormalities in the veins that drain the testicles. There may be a blockage in the veins, or a problem with the valves in the veins. The valves are flaps that prevent blood flowing in the wrong direction.

The abnormal veins do not circulate blood as efficiently as normal veins. This leads to a build-up of excess blood in the veins, which makes them swell.

During puberty (when the body matures sexually), blood flow increases to the testicles and they grow larger. This can make varicoceles more noticeable.


During pregnancy, a male baby's testicles develop inside his abdomen (tummy). Once formed, the testicles pass down through a passage and into the scrotum (the loose sac of skin that contains the testicles).

Usually, the passage closes before birth, but in some cases it stays open. If the passage remains open, fluid can pass from the abdomen into the scrotum, causing the swelling associated with a hydrocele.

In most cases, the fluid is absorbed into the surrounding tissue during the child's first year or two of life, and the hydrocele disappears.

Hydroceles that develop in men or older boys may be caused by inflammation (redness and swelling) of the scrotum, which is the result of:

  • an injury
  • an infection
  • a tumour (growth)

Epididymal cysts

The epididymis is a coil-like structure behind the testicles that helps to store and transport sperm. Sometimes, a fluid-filled swelling can appear on the epididymis, although the cause is usually unknown.

Testicular torsion

The testicles hang from a cord known as the spermatic cord. The spermatic cord should be loose enough to allow the testicles some movement within the scrotum but not so loose that they can move too freely.

Some boys are born with a spermatic cord that is too loose. This means there is an increased risk of a testicle moving too much and twisting the spermatic cord as a result.

If a spermatic cord becomes severely twisted, the main blood supply for the affected testicle can be interrupted. This is an emergency. If it is not treated immediately, the testicle may die. Immediate surgery is needed to untwist the cord, restore the blood supply and save the testicle.

Testicular torsion is most common among boys aged 13-17, although it can also occur in:

  • men in their 20s
  • unborn babies in the womb
  • newborn babies

Testicular torsion can sometimes occur if there is trauma to the testicle, such as in an accident. However, most cases happen for no apparent reason. Testicular torsion may be more likely if you have a history of undescended testicles (where a boy is born without one or both testicles in their scrotum).

Other causes

Other causes of testicular lumps or swellings include: 

  • epididymitis – inflammation of the epididymis, which may be caused by a sexually transmitted infection or a urinary tract infection
  • epididymo-orchitis – epididymitis combined with orchitis (inflammation of the testicle), usually due to an infection 
  • inguinal hernia – a piece of your bowel pokes through a weakness in the muscle or surrounding tissue wall into your groin (more than a quarter of men will have an inguinal hernia during their lifetime) 

Page last reviewed: 01/10/2012

Next review due: 01/10/2014


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