What is the significance of the fat halo sign?
In the setting of known inflammatory bowel disease, the “fat halo” sign indicates chronic disease characterized by fat deposition with the submucosa with relative hyperattenuation of the mucosa and muscularis propria or serosa on CT. On MRI, fat signal intensity is seen in the submucosa. This finding is present in up to 60% of patients with UC, but in only 8% of patients with Crohn’s disease. Of note, this finding is nonspecific and can be seen in nondiseased individuals as well.
