The Comb Sign

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A 20-year-old woman with no significant past medical history presented with a 3-year history of intermittent cramping lower abdominal pain, worse post-prandial, with no change in bowel habit, nausea, or vomiting. Physical examination revealed a soft abdomen with tenderness to deep palpation across the periumbilical area. C-reactive-protein was mildly elevated at 31 mg/L and normal erythrocyte sedimentation rate of 5 mm/h. Gastroscopy and colonoscopy were normal. Computed tomography scan of the abdomen revealed a long segment of abnormality, approximately 60 cm, involving the mid small bowel and Comb sign was present (Figures A and B, arrows). A further magnetic resonance enterography revealed circumferential bowel wall thickening (Figure C, arrow). Subsequent deep intubation retrograde endoscopy revealed several scattered ulcers. Small bowel and colon biopsies revealed noncaseating granulomas (Figure D, arrow) consistent with Crohn’s disease. Comb sign is the engorgement of the mesenteric vessels with vascular dilatation, tortuosity with spacing of the vasa recta, and prominence of surrounding mesenteric fat resembling a comb and is associated with Crohn’s disease. However, it is not pathognomonic of Crohn’s disease and can also be associated with other inflammatory diseases of the bowel or vasculitis. Comb sign can be used to differentiate active inflammatory bowel disease from lymphoma, which is more likely to be hypovascular.