IS case 546: Comb sign

Alok Bhatt, MD

University of Rochester

Imaging Sciences URMC 2010
Publication Date: 2010-09-18


Patient is a 41-year-old female, with history of Crohn's disease, who presented to the emergency room complaining of right lower quadrant abdominal pain.


CT scan of the abdomen and pelvis demonstrated increased enhancement and wall thickening of the distal small bowel with areas of adjacent fat stranding and thickening of the vasa recta consistent with Crohn's disease flare.


Comb sign


Crohn's disease is characterized as a chronic granulomatous inflammation of the GI tract with periods of remission and relapse. There is inflammation of the bowel mucosa, bowel wall, and mesentery.

CT findings of Crohn's disease include:


Involvement of the small bowel, more specifically, terminal ileum (seen in about 80% of cases), with circumferential wall thickening measuring about 1-2 cm. 2.

Acutely inflamed bowel shows intense wall enhancement after IV contrast with the degree of enhancement correlating with the severity of inflammation. 3.

Hyperemic thickening and swelling of the vasa recta produces a comb-like appearance extending from the bowel wall into the mesenteric fat, known as the "comb sign". 4.

"Skip lesions" may be present (alternating areas of normal bowel and inflamed bowel). 5.

Fistula formation between bowel loops. 6.

Fibrofatty stranding.


  1. Webb WR, Brant WE, Major NM. Fundamentals of Body CT, 3rd ed. Philadelphia: Saunders, 2006.

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