Snail shell sign: Testicular/ovarian torsion

Abstract

The snail shell sign is seen with torsion of the spermatic cord on ultrasound. Its appearance in the axial plane has been described as a snail-shell, a whirlpool, a doughnut or a storm on a weather map. This is the most sensitive and specific sign for torsion, even more so than absence of intratesticular flow on colour Doppler. 1,2 Testicular torsion occurs in approximately 1 in every 4000 men under the age of 25 years. Torsion of the spermatic cord represents 26-27% of children with acute scrotum (other causes are torsion of the appendix testis and epididymitis in around 50% and 10% respectively). The two most important factors determining testicular damage are the length of time from onset of symptoms to cord detorsion, and the degree of cord twist. Salvage rate of testes after detorsion is reported at 62-85%. However, this does not correspond to salvaged testicular function. Semen analysis is normal in only 5-50% of patients Postulated causes for the low semen quality include consequences of reperfusion injury episodes during previous asymptomatic intermittent torsion or congenital abnormality. 3 The snail shell sign is also used to describe the twisted vascular pedicle in ovarian torsion. 4Ovarian torsion generally occurs in women with moderately enlarged ovaries, often in association with an ovarian cyst. Although more common in premenarchal girls, normal appearing ovaries are involved in up to 46% of torsion cases. 12 to 25% of adnexal torsion cases occur during pregnancy. Torsion occurs less commonly in markedly enlarged ovaries. 5 References 1. Baud C, Veyrac C, Couture A, Ferran J. Spiral twist of the spermatic cord: a reliable sign of testicular torsion. Pediatr Radiol 1998; 28: 950-54. 2. Kalfa N, Veyrac C, Baud C, Couture A, Averous M, Galifer RB. Ultrasonography of the spermatic cord in children with testicular torsion: impact on the surgical strategy. J Urol 2004; 172: 1692-5. 3. Drl ık M, Ko cvara R. Torsion of spermatic cord in children: a review. J Pediatr Urol 2013; 9: 259-66. 4. Vijayaraghavan SB. Sonographic whirlpool sign in ovarian torsion.