Pathological features

Macroscopically in Crohn's disease there may be a swollen, reddened and rubbery bowel with:

• skip lesions - discontinuous sites of pathology along the gastrointestinal tract
• cobblestone ulceration; a result of apthous ulceration progressing to oedema and nodular thickening
• lead pipe thickening - thickened, stiff bowel
• narrowed lumen
• strictures
• 'rose-thorn' narrow-mouthed ulcers which lead to fistulae
• fistulae, often between adherent bowel and/or bladder, vagina, other abdominal organs or the abdominal wall
• mesenteric fat covering serosa (1)
• enlarged mesenteric nodes

Microscopically, there is:

• non-caseating granulomas - not always present
• transmural inflammation and lymphocyte infiltration (1)

Crohn's disease may involve any part of the bowel from the mouth to the anus:

• the terminal ileum is involved in nearly 50% of cases
• jejunoileitis is also seen, but most ileal inflammation usually ends abruptly at the ileocaecal junction
• caecal and right colonic involvement is more common than lesions in the stomach and duodenum

Reference:

• (1) Van Assche G et al. The second European evidence-based consensus on the diagnosis and management of Crohn's disease: Definitions and diagnosis. Journal of Crohn's and Colitis 2010; 4:7–27