Perianal complications of Crohn disease: MR imaging findings

The aim of this study was to revisit anal anatomy, to explain surgical terminology in perianal complications of Crohn disease, and to show the MR imaging findings of perianal fistulas and abscesses. To this end more than 200 patients were studied using surface coils (Helmholtz; phased array) at 1.0 and 1.5 T. Transverse and coronal T1- and T2-weighted images were obtained. Parks' classification was used to describe perianal abscesses and fistulas. This pictorial essay shows the normal anal anatomy and pathologic findings such as subcutaneous, para-anal, ischiorectal, intersphincteric, and supralevatoric abscesses and fistulas. MR imaging with surface coils is well suited to showing the anal anatomy and to reliably describing perianal abscesses and fistulas according to surgical terminology.