Paris classification of pediatric Crohn disease

	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
	A1	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
	L4	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
Growth		G₁	Growth delay (impaired linear growth)^Δ

The Paris classification of inflammatory bowel disease in children is a modification of the Montreal classification used for adults. This classification incorporates age categories within the pediatric range and includes categories for growth effects. In both the Montreal and Paris classification systems, upper GI disease (L4 and L4a/L4b) may coexist with lower GI disease (L1, L2, or L3). Disease extent is based on macroscopic appearance of mucosal ulceration or bowel wall thickening on radiography. The presence of mucosal erythema and/or granularity is not sufficient to be considered evidence of involvement.

GI: gastrointestinal.
* Stricturing disease refers to constant luminal narrowing demonstrated by radiologic, endoscopic, or surgical examination, combined with prestenotic dilation and/or obstructive signs or symptoms.
¶ Penetrating disease refers to bowel perforation, intra-abdominal fistulas, inflammatory masses, and/or abscesses at any time in the course of the disease, and not a secondary postoperative intra-abdominal complication. This excludes isolated perianal or rectovaginal fistulae.
Δ Impaired linear growth is manifested by either height Z-score at diagnosis that is significantly less than expected or a significant reduction in height Z-score since diagnosis.

Modified with permission from: Levine A, Griffiths A, Markowitz J, et al. Pediatric modification of the Montreal classification for inflammatory bowel disease: The Paris classification. Inflamm Bowel Dis 2011; 17:1314. DOI: 10.1002/ibd.21493. Copyright © 2011 Crohn's and Colitis Foundation of America, Inc. Unauthorized reproduction of this material is prohibited.

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