Table 12.

Paris classification of CD

Age at the time of diagnosis	A1a	0–9 years
	A1b	10–16 years
	A3	17–40 years
	A3	≥ 41 years
Extent of involvement	L1	Localized lesions in the ileum with or without the cecum in the anorectal one-third
	L2	Colorectal lesions
	L3	Iliac and colorectal lesions
	L4a	Upper lesion on the oral side above the Treitz ligament
	L4b	Upper lesion anorectally above the Treitz ligament and more orally than the terminal one-third of the ileum
Disease state	B1	Inflammatory lesions without stenosis or perforation
	B2	Stenotic lesions
	B3	Perforating lesions
	B2B3	Stenotic/perforating lesions
	P	With anal lesions (only with hemorrhoids, anal canal ulcers, or abscesses)
Growth	G0	Stunted growth not present
	G1	Stunted growth present

CD Crohn’s disease