The Vienna classification is used to describe the clinical phenotype for a patient with Crohn's disease. It should be viewed as a dynamic model that can change as the disease evolves.
Parameters:
(1) age at diagnosis (A)
(2) location (L) based on maximal extent of the disease prior to the first bowel resection
(3) behavior (B)
Parameter
Finding
Designation
age at diagnosis
< 40 years
A1
>= 40 years
A2
location
terminal ileum with or without involvement of the cecum
L1
colon
L2
both ileum and colon
L3
upper GI tract
L4
behavior
non-stricturing, non-penetrating
B1
stricturing (without penetrating features)
B2
penetrating
B3
where:
• Penetrating disease involves intra-abdominal or perianal fistula, perianal ulcer, inflammatory mass, or abscess, with or without strictures.
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