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Gastroenterology

Montreal classification of inflammatory bowel disease calculator

Enter the published formula inputs below to calculate and interpret this score.

Clinical inputs

Disease
years

Allowed range: 0–100 years

Quick picks

Crohn disease only. A1 is 16 years or younger, A2 is 17 through 40 years, and A3 is older than 40 years. Age does not classify ulcerative colitis.

Crohn location

L1 is terminal ileum, L2 is colon, L3 is ileocolon, and L4 alone is isolated upper gastrointestinal disease. Ignored for ulcerative colitis.

Crohn behavior
Ulcerative colitis extent

Maximal endoscopic extent. E1 is distal to the rectosigmoid junction, E2 is distal to the splenic flexure, and E3 is proximal to the splenic flexure. Ignored for Crohn disease.

Ulcerative colitis severity

S0 is clinical remission. S1 is mild: four or fewer bloody stools daily, no fever, pulse under 90 per minute, hemoglobin at least 105 g/L, and ESR under 30 mm/h. S2 is between mild and severe. S3 is severe: at least six bloody stools daily, pulse at least 90 per minute, temperature at least 37.5°C, hemoglobin under 105 g/L, and ESR at least 30 mm/h.

Result

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Clinical inputs

  • Disease
  • Age at diagnosis (years)Accepted range: 0 to 100
  • Crohn location
  • Upper-tract modifier on L1 to L3
  • Crohn behavior
  • Perianal modifier
  • Ulcerative colitis extent
  • Ulcerative colitis severity

Primary source

Silverberg MS et al. Toward an integrated clinical, molecular and serological classification of inflammatory bowel disease: report of a Working Party of the 2005 Montreal World Congress of Gastroenterology. Can J Gastroenterol. 2005;19(Suppl A):5A-36A. DOI: 10.1155/2005/269076. PMID: 16151544. Crohn age at diagnosis: A1 is 16 years or younger, A2 is 17 through 40 years, and A3 is older than 40 years. Location: L1 terminal ileum, L2 colon, L3 ileocolon, L4 isolated upper gastrointestinal disease. L4 is also a modifier on L1 through L3 when disease is proximal to the terminal ileum. Behavior: B1 non-stricturing non-penetrating, B2 stricturing, B3 penetrating, with perianal modifier p. Ulcerative colitis extent is the maximal endoscopic extent: E1 distal to the rectosigmoid junction, E2 distal to the splenic flexure, E3 proximal to the splenic flexure. Severity: S0 clinical remission, S1 mild, S2 moderate, S3 severe, using the Truelove and Witts and American College of Gastroenterology bounds printed in that report. Age is not used for ulcerative colitis. The numeric result is the age band for Crohn disease and the extent band for ulcerative colitis. The phenotype line carries the letter code. (2005)

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