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Normal and twisted testicular appendages. (a) Longitudinal power Doppler image of a 10-year-old boy with a hydrocele shows the normal appendix testis as a round structure (arrow) that is isoechoic relative to the testis and is supplied by a branch of the capsular artery. (b) Longitudinal US scan of the left hemiscrotum in a patient with scrotal pain and swelling shows a highly echogenic well-defined mass (arrows) at the upper pole of the epididymis (E). The mass represents a twisted epididymal appendage. T = testis. (c) Color Doppler image of the same patient shows that the twisted appendage is avascular (arrows). Mild reactive hypervascularity is seen at the epididymal head and scrotal tunics.

http://radiographics.rsna.org/content/25/5/1197.figures-only