left renal vein at a right angle; (c) the left testicular artery in some men arches over the left renal vein, thereby compressing it; and (d) the descending colon distended with feces may compress the left testicular vein. The US appearance of varicocele consists of multiple, hypoechoic, serpiginous, tubular like structures of varying sizes larger than 2 mm in diameter that is usually best visualized superior or lateral to the testis [Fig. 27a]. Color flow and duplex Doppler US optimized for low-flow velocities help confirm the venous flow pattern, with phasic variation and retrograde filling during a Valsalva's maneuver [Fig. 27b]. Intratesticular varicocele may appear as a vague hypoechoic area in the testis or mimics tubular ectasia. With color Doppler, this intratesticular hypoechoic area also showed reflux of vascular flow during Valsalva's maneuver [Fig. 28]. Undescended testis Normally the testes begin its descent through the inguinal canal to the scrotum at 36 weeks’ of gestation and completed at birth. Failure in the course of testes descent will result in undescended testes (Cryptorchidism). Undescended testis is found in 4% of full-term infants but only 0.8% of males at the age of 1 year have true cryptorchidism. Although an undescended testis can be found anywhere along the pathway of descent from the retroperitoneum to the scrotum, the inguinal canal is the most common site for an undescended testis. Deviation of testis from the normal pathway of descent will result in ectopic testis that is commonly seen in pubopenile, femoral triangle and perineal regions. Besides infertility, undescended testes carry an increased risk of malignancy even for the normally located contralateral testis. The risk of malignancy is estimated to be as high as 10 times the normal individual with seminoma being the most common malignancy. The incidence of infertility is decreased if surgical orchiopexy is carried out before the 1–3 years but the risk of malignancy does not change. Because of the superficial location of the inguinal canal in children, sonography of undescended testes should be performed with a high frequency transducer. At ultrasound, the undescended testis usually appears small, less echogenic than the contralateral normal testis and usually located in the inguinal region [Fig. 29]. With color Doppler, the vascularity of the undescended testis is poor. Testicular appendiceal torsion At sonography, the appendix testis usually appears as a 5 mm ovoid structure located in the groove between the testis and the epididymis. Normally