Torsion of the appendix testis

Imaging description A longitudinal ultrasound of the right scrotum (Fig. 73.1) in a 13-year-old boy with gradual onset of testicular pain demonstrates a well-defined oval hypoechoic avascular structure located in the groove between the testis and epididymis. There was mild hyperemia of the testis and epididymis, which were otherwise normal in appearance. A moderate hydrocele and scrotal wall edema was also noted. These findings were suggestive of torsion of the appendix testis. Importance. Testicular appendages are remnants of embryonic mesonephric and paramesonephric ducts and consist of vascularized connective tissue. Five types of appendages have been identified. The appendix testis is a tiny structure, 1–7 mm in size, located at the upper pole of the testis, in the groove between the testis and epididymis. It has similar echogenicity to the testis and may be oval or sessile and less commonly pedunculated. It is present in 92% of patients and is the commonest appendage to undergo torsion. The appendix epididymis is located at the head of the epididymis, is commonly pedunculated, and is less frequently seen on ultrasound. The other appendages are difficult to identify on ultrasound imaging.