Figure 4.

Extrasphincteric fistula at 6 o'clock with abscess. Sagittal (a) and axial (b) view of anal canal on 3D-EAUS showing at 6 o'clock (6) the proximal origin of an extrasphincteric fistula which drains into a big extrasphincteric abscess (calibers 1–3). On (c) and (d) sagittal and axial view, respectively, of anal and perianal region on MRI which is indispensable to demonstrate the complete extension of the extrasphincteric abscess (black star) and the appearance of edematous surrounding tissues.