Fig. 1

The collagen area fraction for severe fibrostenosis was calculated as a histological fibrosis score of 4 in patients with colonic CD. a The fibrotic areas in the bowel wall that were stained using Masson trichrome are shown as a distinct blue region, and the blood, muscle, and inflammatory cells are shown in red. b The area of the bowel wall and (c) the area of collagen fiber within the bowel wall are automatically identified and divided by the area of the whole picture to the yield area ratio. The collagen area fraction = [30.22% / 64.07%] × 100% = 47.17%. CD, Crohn’s disease