Table 2.

Montreal classification of inflammatory bowel disease

IBD	Montreal classification
Crohn disease
Age of diagnosis	A1 below 16 yr
	A2 between 17 and 40 yr
	A3 above 40 yr
Location	L1 ileal
	L2 colonic
	L3 ileocolonic
	L4 isolated upper disease
Behaviour	B1 non-stricturing, non-penetrating
	B2 stricturing
	B3 penetrating
	P perianal disease
Ulcerative colitis
Extent	E1
	Ulcerative proctitis (distal to the rectosigmoid junction)
	E2
	Left sided UC (distal to the splenic flexure)
	E3
	Extensive UC (proximal to the splenic flexure)
Severity	S0
	Clinical remission (asymptomatic)
	S1
	Mild UC: Passage of four or fewer stools/d with or without blood, absence of any systemic illness, and normal inflammatory markers
	S2
	Moderate UC: Passage of more than four stools per day but with minimal signs of systemic toxicity
	S3
	Severe UC: Passage of at least six bloody stools daily, pulse rate of at least 90 beats/min, temperature of at least 37.5 °C, haemoglobin of less than 10.5 g/100 mL, and ESR of at least 30 mm/h

IBD: Inflammatory bowel disease; ESR: Erythrocyte sedimentation rate; UC: Ulcerative colitis.