What is spermatic cord torsion, and what are its US imaging features?
Spermatic cord torsion (sometimes given the misnomer of testicular torsion) is a surgical emergency. It is secondary to twisting of the spermatic cord between 90° and 720°, which leads to venous obstruction followed by arterial obstruction, potentially leading to testicular infarction. In most cases, the testicles are viable if treated within 6 hours with detorsion and subsequent orchiopexy.
Intravaginal torsion occurs in 90% of cases and is predisposed by the congenital “bell-clapper” deformity (found in ≈10% of males) where the tunica vaginalis completely surrounds the testicle and epididymis. The testicle and epididymis are then not anchored posteriorly and can freely rotate around their vascular pedicle within the tunica vaginalis. Intravaginal torsion typically occurs in adolescents and young adults, most often during the second decade of life.
Extravaginal torsion, which is much less common, occurs at the level of the inguinal ring and is typically seen in neonates.
Doppler US is the major diagnostic imaging test used for detection and diagnosis of this condition, and it has a sensitivity of ≈90%. On US, the key diagnostic feature is decreased or absent testicular and epididymal blood flow on Doppler US, although blood flow may be preserved with partial, early, or transient torsion, or may even be increased with detorsion and reactive hyperemia. Other imaging findings may include: increased testicular and epididymal size; homogeneous testicular echotexture early on, which is a predictor of testicular viability; increased testicular heterogeneity over time, which is suggestive of necrosis; visualization of a twisted spermatic cord with a “cord knot” or swirling “whirlpool” appearance; and a reactive hydrocele