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. Author manuscript; available in PMC: 2011 Oct 1.
Published in final edited form as: Gastroenterology. 2010 Jul 14;139(4):1147–1155. doi: 10.1053/j.gastro.2010.06.070

Appendix 1.

Montreal modification of the Vienna classification of Crohn's disease (adapted from Silverberg MS, et al16)

Age at diagnosis (A)
A1 16 years or younger
A2 17-40 years
A3 Over 40 years
Location (L) Upper GI modifier (L4)
L1 Terminal Ileum L1 + L4 Terminal ileum + Upper GI
L2 Colon L2 + L4 Colon + Upper GI
L3 Ileocolonic L3 + L4 Ileocolonic + Upper GI
L4 Upper GI
Behavior (B) Perianal disease modifier (p)
B1 Non-stricturing, non-penetrating B1p Non-stricturing, non-penetrating + perianal
B2 Stricturing B2p Stricturing + perianal
B3 Penetrating B3p Penetrating + perianal