Causes of CT Bowel Fat Halo Sign

CT Bowel Fat Halo Sign

Seen in 

1. Chronic Inflammatory Bowel Disease

2. Cytoreductive therapy

3. GVHD.

4. Normal patients ~20% of normal, with increased BMI can have this sign positive.

"When seen in both the small and large bowel, the halo sign has been considered specific evidence of Crohn’s disease. When only the colon is affected, the degree and geographic distribution

of bowel wall thickness are signs used to distinguish ulcerative colitis from Crohn’s disease. '

(Gore RM, Balthazar EJ, Ghahremani GG, MillerFH. CT features of ulcerative colitis and Crohn's, AJR, 1996)