Fig. 9
A 53-year-old man with purulent drainage and clinical diagnosis of perianal inflammation. Axial images (b,c) from urgent contrast-enhanced MDCT show solid circumferential thickening of the anal canal (arrowheads) associated with abscess collections with mixed gas-fluid content (*) and fistulas crossing the ischioanal space. Surgical examination under anaesthesia including biopsies revealed ulcerated SCAC with superinfection. After surgical drainage and subsequent chemo-radiotherapy, MRI (c) shows complete resolution of both inflammatory and neoplastic changes with residual T2-hypointense fibrotic tracks