Ultrasound of Torsion of the Appendix Testis

In this radiology lecture, we review the ultrasound appearance of torsion of the appendix testis and appendix epididymis!

Key teaching points include:

  • Appendix testis is a vestigial appendage usually located between upper pole of testis and head of epididymis.
  • AKA hydatid of Morgagni, the appendix testis is commonly present as a normal finding.
  • Appendix epididymis typically arises from epididymal head.
  • Both scrotal appendages are often pedunculated which increases risk of torsion.
  • Torsion occurs when appendage twists, occluding blood supply.
  • Torsion of the appendix testis is one of most common causes of acute scrotal pain in prepubertal children.
  • Peak age 7-12 years old, but can occur at any age.
  • Normal appendix testis: Oval-shaped, less than 6 mm in size, homogeneously isoechoic to epididymis, and demonstrates little to no blood flow on color Doppler.
  • Torsed appendix testis: 6 mm or larger in size, variable echogenicity, hypoechoic before 24 hours, hyperechoic or heterogeneous after 24 hours.
  • In setting of appendix torsion, hyperemia of surrounding structures with hydrocele and scrotal wall thickening often present.
  • Torsed appendage can detach and become free floating in scrotum.
  • Patients may present with pain localized to upper pole of testis or epididymis.
  • Physical examination may yield the “blue dot” sign: Small, palpable nodule at superior aspect of testis with bluish discoloration of overlying skin due to ischemic appendix.
  • Cremasteric reflex typically intact, and testicle not high riding (unlike testicular torsion).
  • Hyperemia of surrounding structures can be difficult to differentiate from bacterial epididymitis.
  • However, in children, epididymitis usually secondary to inflammation from direct trauma, torsion of a scrotal appendage, or urine reflux into epididymis. Urine dipstick/urinalysis helpful to differentiate from infection.
  • Treatment: Pain management with analgesics, ice, rest. If not recognized, may be treated unnecessarily with antibiotics. Scrotal exploration may be necessary if testicular torsion cannot be excluded.

References:
Baldisserotto M, Ketzer de Souza JC, Pertence AP, Dora MD. Color Doppler sonography of normal and torsed testicular appendages in children. AJR 2005; 184:1287–1292

To learn more about the Samsung RS85 Prestige ultrasound system, please visit: https://www.bostonimaging.com/rs85-prestige-ultrasound-system-4

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