Crohn disease
Description
- Transmural, granulomatous inflammation, mouth to anus, discontinuous skip lesions
- Distribution: ileocolonic ~40%, ileal ~30%, colonic ~25%, isolated upper GI ~5%
Montreal classification
| Axis | Categories |
|---|---|
| A age at diagnosis | A1 <=16 / A2 17-40 / A3 >40 |
| L location | L1 ileal / L2 colonic / L3 ileocolonic / L4 isolated upper GI (modifier) |
| B behaviour | B1 non-stricturing non-penetrating / B2 stricturing / B3 penetrating; +p = perianal |
- Behaviour is not static - B1 progresses to B2/B3 in ~50% over 20 yrs. The point of early effective therapy is to stop that.
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