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

Key teaching points include:
1) Appendix testis is a vestigial appendage usually located between upper pole of testis and head of epididymis.
2) AKA hydatid of Morgagni, the appendix testis is commonly present as a normal finding.
3) Appendix epididymis typically arises from epididymal head.
4) Both scrotal appendages are often pedunculated which increases risk of torsion.
5) Torsion occurs when appendage twists, occluding blood supply.
6) Torsion of the appendix testis is one of most common causes of acute scrotal pain in prepubertal children.
7) Peak age 7-12, but can occur at any age.
8) 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.
9) Torsed appendix testis: 6 mm or larger in size, variable echogenicity, hypoechoic before 24 hours, hyperechoic or heterogeneous after 24 hours.
10) In setting of appendix torsion, hyperemia of surrounding structures with hydrocele and scrotal wall thickening often present.
11) Torsed appendage can detach and become free floating in scrotum.
12) Patients may present with pain localized to upper pole of testis or epididymis.
13) 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.
14) Cremasteric reflex typically intact, and testicle not high riding (unlike testicular torsion).
15) Hyperemia of surrounding structures can be difficult to differentiate from bacterial epididymitis.
16) 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.
17) 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

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