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Spermatocele

Last revised by Dr Henry Knipe on 23 Dec 2021

Spermatoceles are a common type of extratesticular cyst (occasionally intratesticular) and represent cystic dilatation of tubules of the efferent ductules in the head of the epididymis.

Usually, a painless, incidental finding but can present as a mass lesion if large 3.

Spermatoceles are usually unilocular but can be multilocular/septated and may be associated with a prior vasectomy. They are more common than epididymal cysts but can appear very similar. 

The exact cause of spermatoceles remains unclear but is thought to be due to blockage of the epididymal ducts with proximal dilatation. This may be idiopathic or secondary to an infectious or inflammatory process 3

At sonographic examination, spermatoceles are well-defined epididymal hypoechoic lesions usually measuring 1-2 cm and demonstrating posterior acoustic enhancement. They are usually irregular, with fine low-level internal echoes and sometimes septations. 

General imaging differential considerations include:

  • epididymal cyst
    • unlike epididymal cysts, spermatoceles often contain low-level echogenic proteinaceous fluid and spermatozoa
    • spermatoceles can be septate
    • they can however be anechoic and thus indistinguishable from epididymal cysts
  • ectasia of rete testes: intratesticular spermatocele communicates with the seminiferous tubules, however, ectatic rete testes do not communicate directly
  • intratesticular simple cyst: simple cysts are usually smooth-walled and anechoic, while spermatoceles show irregular wall with low-level echoes

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Cases and figures

  • Case 1: multilocular spermatocoele
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  • Case 2: unilocular spermatocoele
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