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Toronto Notes 2019 Small and Large Bowel Gastroenterology G19 Inflammatory Bowel Disease
Definition
• complex,multifactorialetiology
• mostlikelyasustainedresponseoftheimmunesystem,perhapstoentericflora
• lackofappropriatedown-regulationofimmuneresponsivenessafteraninfectioninagenetically
predisposed individual
Genetics
• increasedriskofbothUCandCDinrelativesofpatientswitheitherdisease,especiallysiblings,early onset disease
■ familial risk greater if proband has CD rather than UC
• likelypolygenomicpattern:9genelociareassociated
• CARD15/NOD2genemutationassociatedwithCD(relativeriskinheterozygoteis3,inhomozygote
is 40), especially Ashkenazi Jews, early onset disease, ileal involvement, fistulizing and fibrostenotic or stricturing disease
■ CARD15 gene product modulates NFκβ, which is required for the innate immune response to microbial pathogens, best expressed in monocytes-macrophages
Clinical Features
Table 10. Clinical Differentiation of Ulcerative Colitis from Crohn’s Disease
Location
Rectal Bleeding Diarrhea
Abdominal Pain
Fever
Urgency/Tenesmus
Palpable Mass
Recurrence After Surgery
Endoscopic Features Histologic Features
Radiologic Features
Complications Colon Cancer Risk
Crohn’s Disease
Any part of GI tract
Small bowel + colon: 50% Small bowel only: 30% Colon only: 20%
Uncommon; possible if colonic disease
Less prevalent, large volume, watery
Usually non-bloody (may be bloody, particularly if distal colonic involvement)
Post-prandial/colicky
Common
Uncommon (unless rectum involved) Frequent (25%), RLQ
Common
Segmental inflammation, ulcers (aphthous, stellate, linear), patchy lesions, pseudopolyps, cobblestoning
Transmural distribution with skip lesions Focal inflammation
± noncaseating granulomas, deep fissuring + aphthous ulcerations, strictures Glands intact
Cobblestone mucosa
Frequent strictures and fistulae
AXR: bowel wall thickening “string sign”
Strictures, fistulae, perianal disease Increased if >30% of colon involved
Ulcerative Colitis
Isolated to large bowel
Always involves rectum, may progress proximally
Very common (90%)
Frequent, mucous, bloody, small volume stools
Uncommon; predefecation
Uncommon
Common
Rare (if present, often related to cecum full of stool) None post-colectomy (with permanent ileostomy)
Continuous diffuse inflammation, erythema, friability, loss of normal vascular pattern, pseudopolyps
Mucosal distribution, continuous disease (no skip lesions)
Architectural distortion, gland disruption, crypt abscess
Granulomas absent
Lack of haustra
Strictures rare; need to rule out complicating cancer
Toxic megacolon
Increased except in proctitis