Fig. 20.

Extensive cryptogenic perianal inflammation in a 56-year old diabetic man with fever. Axial post-contrast CT image (a) revealed perineal abscess (arrowheads) very similar to that depicted in Fig. 15. Additional MRI including axial STIR (b), post-gadolinium axial fat-suppressed (c) and coronal (d) T1-weighted images showed extensive inflammatory signal abnormalities and hyperenhancement (+) surrounding the anus, involving the right sphincter complex and obturator internus (*) muscles, and extending to the ischioanal fossa. Tiny abscess collections (arrows in b and c) were present. Topography of infection, sparing of prostate and corpora cavernosa, and clinical examination were inconsistent with complicated UTI