Three-dimensional endoanal ultrasound should be considered as first-line diagnostic tool in the preoperative work-up for perianal fistulas: The authors reply to the letter: Mathew RP, Patel V, Low G. Caution in using 3D-EAUS as the first-line diagnostic tool in the preoperative work up for perianal fistulas. Radiol Med 2020;125:155–156

In the preoperative work-up of patients with anorectal fistulas, 3D-EAUS may represent the first-line diagnostic tool, showing high diagnostic accuracy in the evaluation of internal openings, primary tracks and secondary extension. In the cases of fistulas classified as complex by 3D-EAUS, MRI may be indicated as adjunctive diagnostic imaging examination, to more accurately detect the fistulas’ secondary extensions, and so, to more carefully describe the fistulas’ complete anatomy.