Clostridium difficile colitis. (a) Coronal contrast-enhanced mixed CT image shows wall thickening throughout the colon, with enhancing mucosa and prominent vasa recta (arrows) representing C difficile pancolitis. (b) Coronal iodine overlay image highlights increased enhancement in the mucosa and vasa recta (arrows). (14) In a patient with ulcerative colitis, axial contrast-enhanced mixed CT image (a) shows bowel wall thickening and mucosal enhancement (arrow), findings that are more conspicuous on an iodine overlay image (b).