Categories used in Montreal classification (adults) | Modified categories used in Paris classification (children and adolescents) | Definition | |
Age at diagnosis | A1 | A1a | 0 to <10 years |
A1b | 10 to <17 years | ||
A2 | 17 to 40 years | ||
A3 | >40 years | ||
Location | L1 | Distal 1/3 of the ileum, with or without limited cecal disease | |
L2 | Colonic | ||
L3 | Ileocolonic | ||
L4 | L4a | Upper GI disease, proximal to the ligament of Treitz | |
L4b | Upper GI disease, between the ligament of Treitz and the distal 1/3 of the ileum | ||
Behavior | B1 | Nonstricturing, nonpenetrating | |
B2 | Stricturing* | ||
B3 | Penetrating¶ | ||
B2B3 | Both penetrating and stricturing disease*¶, either at the same or different times | ||
P | Perianal disease modifier | ||
Growth | G0 | No growth delay | |
G1 | Growth delay (impaired linear growth)Δ |
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