Table 7

Montreal and Paris classification in Crohn’s disease

Montreal29 Paris23
Age at diagnosis (years)A1<17A1a<10
Location*L1Terminal ileal±limited caecal diseaseL1Distal 1/3 ileum±limited caecal disease
L4Isolated upper disease†L4aUpper disease proximal to ligament of Treitz†
L4bUpper disease distal to ligament of Treitz and proximal to distal 1/3 ileum†
BehaviourB1Non-stricturing, non-penetratingB1Non-stricturing, non-penetrating
B2B3Both penetrating and stricturing disease, either at the same or different times
PPerianal disease modifier‡PPerianal disease modifier‡
GrowthG0 No evidence of growth delay
G1 Growth delay
  • B2: Stricturing defined as the occurrence of constant luminal narrowing demonstrated by radiologic, endoscopic, or surgical examination combined with pre-stenotic dilatation and/or obstructive signs or symptoms but without evidence of penetrating disease.

  • B3: Penetrating disease: defined as the occurrence of bowel perforation, intra-abdominal fistulae, inflammatory masses and/or abscesses at any time in the course of the disease, and not secondary to postoperative intra-abdominal complications (excludes isolated perianal or rectovaginal fistulae).

  • *Defined as endoscopic or macroscopic extent.

  • †Upper disease in Montreal classification describes disease proximal to the terminal ileum. In both Montreal and Paris: L4 and L4a/b may coexist with L1, L2, L3.

  • ‡Perianal abscesses, ulcers or fistulae (but not skin tags or fissures).