Comb sign in Crohn's disease.

We present a case of a 13-year-old boy with Crohn's disease (CD) who presented with abdominal pain and diarrhea. On examination, there was tenderness on the lower abdomen. Laboratory examinations showed elevated inflammatory parameters. A CT scan showed active inflammation of the ileum and rectosigmoid colon with the comb sign. A diagnosis of exacerbation of CD was made. The comb sign refers to hypervascularity of the mesentery with vascular dilatation, tortuosity, and wide spacing of the vasa recta that are aligned as the teeth of a comb. This sign is not always pathognomonic for CD; however, it may help identification of acute exacerbation in known CD and differentiating active CD from hypovascular disease such as lymphoma. The comb sign can be highly correlated with the endoscopic severity rather than mural thickening in CD.