Inflammatory bowel disease

Crohn's disease

Topic Completed: 1 May 2013

Minor changes: 3 December 2021

Copyright: 2003-2022,, Inc.

PubMed Search: Crohn disease [title] of colon

Hanni Gulwani, M.B.B.S.
Page views in 2021: 35,371
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Cite this page: Gulwani H. Crohn's disease. website. Accessed January 19th, 2022.
Definition / general
  • Transmural granulomatous disease affecting GI tract from esophagus to anus but discontinuous (Wikipedia, eMedicine #1, #2)
  • Also called regional enteritis because it affects sharply delineated segments, or granulomatous colitis due to granulomas
  • Primarily affects Western populations with prevalence of 3 per 100,000, peaks in teens / twenties and at ages 50 - 69
  • More common in whites (HLA-DR1/DQw5), Jews, smokers; monozygotic twins have 30 - 50% concordance
  • Usually involves small intestine; 40% of patients have colon involvement
Diagrams / tables

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Comparison of patients with Crohn's disease vs tuberculosis

Clinical features
  • Symptoms: episodic mild diarrhea, fever, pain; may be precipitated by stress; if colon affected, may have anemia
  • 20% have abrupt onset of symptoms resembling acute appendicitis or bowel perforation
  • Extraintestinal symptoms: migratory polyarthritis, sacroiliitis, ankylosing spondylitis, erythema nodosum, clubbing of fingertips, primary sclerosing cholangitis (not as common as with ulcerative colitis); occasionally uveitis, pericholangitis and renal disorders secondary to periureteral fibrosis
  • Complications: fibrosing strictures (common in terminal ileum); fistulas to loops of bowel, bladder, vagina and perianal skin; also protein losing enteropathy, generalized malabsorption, vitamin B12 deficiency, bile salt malabsorption with steatorrhea, toxic megacolon (4%), carcinoma (see here)
  • Patients with isolated colonic Crohn's disease present at a significantly older age at diagnosis, have significantly shorter duration of colitis before surgical resection, compared to those with ileocolonic disease at onset (Mod Pathol 2012;25:295); also have higher proportion of subtotal, total or left sided colitis and significantly fewer strictures / stenosis, pericolonic adhesions, pyloric metaplasia
  • Definitive diagnosis (per Sternberg): transmural lymphoid aggregates in areas not deeply ulcerated, nonnecrotizing granulomas; suggestive features are skip lesions, linear ulcers, cobblestoning, fat wrapping or terminal ileum inflammation
  • Often requires multiple biopsies; difficult to diagnosis without terminal ileum involvement
Case reports
  • Medical therapy (steroids, antibiotics); may need surgery eventually, although often recurs in pouch; involvement of resection margins doesn’t correlate with recurrence
Gross description
  • Dull and granular serosa, creeping fat (mesenteric fat wraps around bowel surface), thick / rubbery intestinal wall (due to edema, inflammation, fibrosis, hypertrophy of muscularis propria), strictures (string sign on barium enema), sharp demarcation of affected segments from uninvolved bowel (skip areas)
  • Aphthous mucosal ulcers coalesce into long, serpentine linear ulcers along bowel axis to acquire cobblestone appearance; fissures in mucosal folds lead to fistulas or sinus tracts
  • Usually rectal sparing; disease overall is less severe in distal vs. proximal colon (i.e. preferential right sided involvement)
Gross images

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Long linear ulcers

Cobblestone pattern

Various images

Microscopic (histologic) description
  • Superficial or deep ulceration with adjacent granulation tissue extending into deep submucosa or below
  • Transmural inflammation with lymphoid aggregates throughout bowel wall; sarcoid-like, noncaseating, poorly formed granulomas in all tissue layers (50 - 70% of cases, may need serial sections to detect), usually adjacent to blood vessels or lymphatics
  • Disease is focal with intervening normal mucosa in bowel and throughout GI tract (mouth to anus)
  • Goblet cells present
  • Initially focal neutrophils in epithelium and overlying lymphoid aggregates and plasmacytosis, then cryptitis, crypt abscesses but usually no neutrophils in lamina propria
  • Mucosa and submucosa are also edematous
  • Often reduplication of muscularis mucosa in diseased segments, fibrosis and thickened bowel wall; may have neuronal hyperplasia; variable Paneth cells and pyloric gland metaplasia
  • Aphthous ulcer: lymphoid follicle with surface erosion
  • Note: Crohn's disease of colon resembles ulcerative colitis but Crohn's colitis also has fistulas / sinus tracts, skip lesions, deep ulcerations, marked lymphocytic infiltration, serositis, granulomas, fewer plasma cells
Microscopic (histologic) images

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Transmural inflammation

Crypt abscesses

Colonic biopsy specimens


Endoscopic biopsy specimen

Differential diagnosis
  • Ischemic colitis
  • Tuberculosis: caseous necrosis, acid-fast bacilli in a minority of biopsy specimens; also differences in size, number and confluence of granulomas, presence of ulcers lined by bands of epithelioid histiocytes and disproportionate submucosal inflammation (J Clin Pathol 2006;59:840)
  • Ulcerative colitis: abnormal rectal biopsy, not transmural, no fissures / fistulas, no granulomas but occasionally may have granulomas around ruptured cysts; may have patchy disease, ileal inflammation, aphthous ulcers or transmural inflammation
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