Epididymal appendix

Epididymal appendices, also known as appendix of the epididymis or appendix epididymis, are an testicular appendage found at the head of the epididymis 1. They represent a developmental remnant of the mesonephric duct (Wolffian duct). In 78% of the cases, it has a stalk configuration and is thus subject to torsion 2.

Normally, epididymal appendages are of no clinical significance, but when torsed they can cause an acute scrotum in children 2. After torsion of its pedicle with resultant infarction, the appendage may detach and wander inside the scrotum and appear as minute mobile particles ("loose bodies") 3.

Ultrasonography with a high-frequency linear transducer can reliably evaluate the appendix testis, including its vascularity. Its reported frequency in ultrasonography is ~12.5% (range 6-17%) 3.

The appendix epididymis, similarly to the appendix testis, is normally oval and pedunculated, although may be sessile in shape 1. They appear iso- or hyperechoic to the epididymal parenchyma. Sometimes, calcifications may be found. In general, the epididymis appendix is best seen when floating in a hydrocele.

When torsed, it is a cause of acute scrotum and imaging differential diagnosis should include:

Anatomy: Abdominopelvic
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Article information

rID: 26487
System: Urogenital
Section: Anatomy
Synonyms or Alternate Spellings:
  • Appendix of the epididymis
  • Appendix epididymis

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Cases and figures

  • Extended Field-of...
    Case 1: epididymis and testis appendages
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  • Case 2: epididymal appendix
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  • Gray-scale high r...
    Case 3: epididymal and testicular appendages
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  • Case 4: torsion of epididymal appendix
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