Are we giving azathioprine too late? The case for early immunomodulation in inflammatory bowel disease

Table 2 Montreal classification of Crohn's disease[13]

Parameter
Age at diagnosis	A1 ≤ 16 yr
	A2 17-40 yr
	A3 ≥ 40 yr
Maximal location of disease prior to first surgery	L1 Terminal ileal
	L2 Colonic
	L3 Ileocolonic
	L4 Upper GI only
	+L4 Additional designation to be added if patient has upper GI and distal disease
Disease behavior	B1 Nonstricturing, nonpenetrating (inflammatory)
	B2 Stricturing
	B3 Penetrating disease
	P = Perianal penetrating disease
	Recommended behavior assessed > 5 yr after diagnosis