tunica albuginea, which is often not visualized in the absence of intrascrotal fluid. However, the tunica is often seen as an echogenic structure where it invaginates into the testis to form the mediastinum testis. In the testis, the seminiferous tubules converge to form the rete testes, which is located in the mediastinum testis. The rete testis connects to the epididymal head via the efferent ductules. The epididymis is located posterolateral to the testis and measures 6–7 cm in length. At sonography, the epididymis is normally iso- or slightly hyperechoic to the normal testis and its echo texture may be coarser. The head is the largest and most easily identified portion of the epididymis. It is located superolateral to the upper pole of the testicle and is often seen on paramedian views of the testis. The normal epididymal body and tail are smaller and more variable in position. The testis obtains its blood supply from the deferential, cremasteric and testicular arteries. The right and left testicular arteries, branches of the abdominal aorta, arise just distal to the renal arteries, provide the primary vascular supply to the testes. They course through the inguinal canal with the spermatic cord to the posterior superior aspect of the testis. Upon reaching the testis, the testicular artery divides into branches, which penetrate the tunica albuginea and arborize over the surface of the testis in a layer known as tunica vasculosa. Centripetal branches arising from the capsular arteries carry blood toward the mediastinum, where they divide to form the recurrent rami that carry blood away from the mediastinum into the testis. The deferential artery, a branch of the superior vesicle artery and the cremasteric artery, a branch of the inferior epigastric artery, supply the epididymis, vas deferens, and peritesticular tissue. Four testicular appendages have been described: the appendix testis, the appendix epididymis, the vas aberrans, and the paradidymis. They are all remnants of embryonic ducts. Among them, the appendix testis and the appendix epididymis are usually seen at scrotal US. The appendix testis is a Müllerian duct remnant and consists of fibrous tissue and blood vessels within an envelope of columnar epithelium. The appendix testis is attached to the upper pole of the testis and found in the groove between the testis and the epididymis. The appendix epididymis is attached to the head of the epididymis. The spermatic cord, which begins at the deep inguinal ring and