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Table 5 Montreal classification for Crohn’s disease phenotype

From: WSES-AAST guidelines: management of inflammatory bowel disease in the emergency setting

Age at diagnosis (A)

Location of disease (L)

Behavior of disease (B)

A1: ≤16 years

A2: 17–40 years

A3: >40 years

L1: ileal

L2: colonic

L3: ileocolonic

L4: modifier for upper gastrointestinal tract

B1: non-stricturing/nonpenetrating

B2: stricturing

B3: penetrating

p: modifier for perianal disease