| Score | Decoding |
| Mayo 0 | normal mucosa or inactive disease |
| Mayo 1 | mild activity (erythema, decreased vascular pattern, mild friability) |
| Mayo 2 | moderate activity (marked erythema, lack of vascular pattern, friability, erosions) |
| Mayo 3 | severe activity (spontaneous bleeding, large ulcerations) |
The Mayo endoscopic subscore is calculated on the more serious injuries observed, by evaluating at least the rectum and sigmoid colon, better if also including the descending colon.
Mayo 0 degree is to be attributed both in case of normality or in case of reparative lesions (scarring or pseudopolyps): in case of presence of pseudopolyps and/or mucosal bridges, to assign the score you need to consider only the flat mucosa interposed (hyperemia and erosions not to be considered if localized only on pseudopolyps).
Mayo 1 degree is characterized by mild inflammation, but substantial, with distortion of the vascular network (not entirely disappeared), focal hyperemia and edema, contact frailty and at maximum 1 single erosion (mucosal break >5 mm).
Mayo 2 degree is identified when at least 2 erosions are present; diffuse erythema and disappearance of the vascular network may or may not also be present.
Mayo 3 degree is given whenever there is at least an ulcer or spontaneous bleeding in a segment.
The presence of deep ulcers, which have prognostic importance, should be considered separately.
| Mayo 0 normal mucosa or inactive disease | ![]() ![]() ![]() |
| Mayo 1 mild disease (erythema, decreased vascular pattern, mild friability) | ![]() ![]() ![]() |
| Mayo 2 moderate disease (marked erythema, lack of vascular pattern, friability, erosions) | ![]() ![]() ![]() |
| Mayo 3 severe disease (spontaneous bleeding, large ulcerations) | ![]() ![]() ![]() |