The split sign: The MRI equivalent of the bell clapper deformity

Abstract

Methods:: The cases of eight patients who underwent MRI and surgery for acute scrotum between January 2010 and January 2017 were evaluated. We recorded whether hyperintense fluid on T₂ weighted images existed between the posterior aspect of the epididymis and the scrotal wall ("split sign") and investigated if it correlated with BCD in surgical findings.

Results:: In one patient without hydrocele, readers were unable to evaluate the anatomy of the tunica vaginalis. Among seven patients with hydrocele, five had the split sign and all were surgically confirmed as BCD. In two patients with hydrocele but no split sign, one had normal scrotal anatomy and the other had a BCD with a necrotic testis adherent to the scrotal wall.

Conclusion:: The split sign on MRI corresponded well to the lack of fixation of the epididymis to the scrotal wall and detected BCD with high sensitivity (5/6).

Advances in knowledge:: A hyperintense area on T₂ weighted image between the posterior aspect of the epididymis and scrotal wall ("split sign") is a useful MRI finding for diagnosing BCD.

Figure 1.

Schema of normal scrotum (a), bell clapper deformity (b), and torsion (c). Note the difference in the attachment site of the tunica vaginalis.

Figure 2.

Cross-sectional anatomy of normal scrotum (a) and bell clapper deformity (b). In bell clapper deformity, the posterior aspect of epididymis is not fixed to the scrotal wall and intravaginal fluid may exist between these two structures (white arrow).

Figure 3.

An example of bell clapper deformity with a hydrocele on MRI (a) and schema (b). The split sign (white arrow), hyperintense area on T₂WI between the posterior aspect of the epididymis and the scrotal wall, is observed. T₂WI, T₂ weighted image.

Figure 4.

An example of a normal scrotum with a hydrocele on MRI (a) and schema (b). The split sign is not observed.

Figure 5.

MR images and schemas of a case with no hydrocele and two cases with no split sign. Patient 8 did not have hydrocele and readers were unable to determine whether BCD was present by the split sign (a). Surgery revealed segmental testicular infarction without BCD. Patient 7 with no split sign was surgically confirmed to have appendix testis torsion without BCD (b). Patient 6 with no split sign had testicular torsion with BCD, whose testicle was necrotic and adherent to the tunica vaginalis (c). BCD, bell clapper deformity.