<prompt> Fat halo sign is associated withUlcerative colitisCrohns diseasePlummer Vinson syndromeChiladiti syndrome  <response>: The Fat halo sign refers to a feature seen on CT examination of the abdomen, and represents infiltration of the submucosa with fat, between the muscularis propria and the mucosa. It is characterized by an inner mucosa and outer muscularis propria and serosa ring of enhancing bowel wall along with a non-enhancing middle layer submucosa. 