Histology scoring system	Reference
Grade 0: Normal mucosa	13,17,18
Grade 1: Subepithelial space at the villous tip
Grade 2: More extended subepithelial space
Grade 3: Epithelial lifting along the villous sides
Grade 4: Denuded villi
Grade 5: Loss of villous tissue
Grade 6: Crypt layer infarction
Grade 7: Transmucosal infarction
Grade 8: Transmural infarction
Grade 0: Normal mucosa	4,8,11,19-21
Grade 1: Sloughing of cells on villous tips
Grade 2: Mid-villous damage
Grade 3: Villi were absent, but crypts were still readily detectable
Grade 4: Complete absence of epithelial structures and transmural necrosis
Grade 0: Normal villus	6,22-31
Grade 1: Villi with tip distortion
Grade 2: Goblet cells and Gugenheims' spaces are missing
Grade 3: Villi with patchy disruption of the epithelial cells
Grade 4: Villi with exposed, but intact lamina propria with epithelial cell sloughing
Grade 5: Lamina propria is exuding
Grade 6: Villi that display hemorrhage or to villi that are denuded
Grade 0: Normal histology	32,33
Grade 1: Slight disruption of the surface epithelium
Grade 2: Epithelial cell loss injury at villus tip
Grade 3: Mucosal vasocongestion, hemorrhage, and focal necrosis with loss of less than half of villi
Grade 4: Damage extending to more than one-half of villi