A 12-year-old boy was evaluated for acute onset of pain in the right scrotum. There was no history of fever or dysuria. On examination, point tenderness was found superior to the right testicle with a bluish skin discoloration. Both testes were normal to palpation. On US, a hypoechoic mass was seen adjacent to the right epididymal head. While the mass had no internal vascularity, there was adjacent hyperemia typical of torsion of a testicular appendage (Figs. 1 and 2).

Fig. 1
figure 1

Hypoechoic mass

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Fig. 2
figure 2

No color flow to mass

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Testicular appendages are remnants of the embryonic mesonephric and paramesonephric ducts. Torsion of testicular appendage is a common cause of acute scrotal pain in prepubertal males [1]. A firm nodule superior to the testicle with bluish discoloration of the skin (blue dot sign) is a characteristic physical finding. US findings are typical as described above. Other associated findings are scrotal skin thickening and reactive hydrocele [1, 2]. US is usually done to rule out testicular torsion and epididymo-orchitis. Management is essentially conservative.