Inflammatory Bowel Disease

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IBD Overview & Patho - Fiery Bowel Basics

  • Inflammatory Bowel Disease (IBD): Chronic, relapsing-remitting GI tract inflammation.
  • Types:
    • Crohn's Disease (CD): Mouth to anus; transmural inflammation; skip lesions.
    • Ulcerative Colitis (UC): Colon only (rectum often involved); mucosal/submucosal; continuous.
  • Epidemiology:
    • Increasing incidence in India.
    • Bimodal age peaks: 15-30 yrs & 50-70 yrs.
  • Pathogenesis: Complex interplay of:
    • Immune dysregulation: Exaggerated T-cell response to normal gut microbiota.
    • Genetic factors: NOD2/CARD15 (strongest for CD), IL23R, ATG16L1.
    • Environmental triggers: Smoking (CD risk ↑, UC protective ↓), diet, NSAIDs, infections.

⭐ > Smoking is protective in Ulcerative Colitis but a risk factor for Crohn's Disease.

Pathogenesis of Inflammatory Bowel Disease

CD vs UC Clincher - Tale of Two Guts

FeatureCrohn's Disease (CD)Ulcerative Colitis (UC)
SiteAny part of GIT (mouth to anus); Terminal ileum commonestColon only; Rectum invariably involved, extends proximally
PatternSkip lesions (discontinuous)Continuous, symmetrical inflammation
DepthTransmural inflammationMucosal & submucosal inflammation
SymptomsRLQ pain, diarrhea (±blood), weight loss, perianal diseaseBloody diarrhea, tenesmus, urgency, abdominal cramps
EndoscopyAphthous ulcers, linear/serpiginous ulcers, cobblestones, strictures, fistulaeDiffuse erythema, granular/friable mucosa, pseudopolyps
RadiologyString sign of Kantor (barium study)Lead pipe colon (loss of haustra)
HistologyNon-caseating granulomas (~50%), lymphoid aggregatesCrypt abscesses, crypt distortion, goblet cell depletion

Endoscopic views of Inflammatory Bowel Disease vs Ulcerative Colitis (friable mucosa, crypt abscess))

⭐ > Extraintestinal manifestations are common in both, but p-ANCA is more associated with UC (60-70%), while ASCA is more with CD (60-70%).

IBD Workup - Diagnostic Deep Dive

  • Key Investigations:
    • Blood: CBC (anemia), ↑ESR/CRP.
    • Stool: Fecal Calprotectin (> 50-100 µg/g suggests inflammation; > 250 µg/g highly indicative of IBD).
    • Serology: ASCA (CD), pANCA (UC) - supportive, not diagnostic.
  • Definitive Diagnosis & Staging:
    • Endoscopy (Ileocolonoscopy) + Biopsy: Gold standard for diagnosis, activity, extent.
    • Upper GI endoscopy for proximal symptoms.
  • Small Bowel & Complication Imaging:
    • CT/MR Enterography: Preferred for small bowel assessment, fistulae, abscesses.
    • String sign of Kantor on barium follow through
    • Barium studies (e.g., "String sign of Kantor" in CD).

⭐ Fecal calprotectin > 250 µg/g is highly specific for IBD, aiding differentiation from Irritable Bowel Syndrome (IBS).

IBD Management - Taming the Flames

  • Goals: Induce & maintain remission.
  • Medical Therapy Pyramid:
    • Base: 5-ASA (Mesalamine) - Mild disease.
    • Middle: Corticosteroids (flares, e.g., Prednisolone 40-60mg), Immunomodulators (AZA, MTX - maintenance, steroid-sparing).
    • Apex: Biologics (Anti-TNF, Anti-integrin, Anti-IL12/23) - Moderate-severe, refractory.
  • Acute Severe UC: IV steroids. No response in 3-5 days? → Rescue (Infliximab/Cyclosporine) or colectomy.
  • Surgery: Complications (fistulae, strictures, dysplasia/cancer), refractory disease.

⭐ For acute severe UC refractory to IV steroids, Infliximab is a common rescue therapy before considering colectomy.

IBD Fallout - Gut & Beyond

  • Gut Complications: Strictures, fistulas, abscesses. Toxic megacolon (UC > CD). Colorectal cancer (CRC) risk ↑ (duration/extent dependent).
  • Extra-intestinal Manifestations (EIMs):
    • MSK: Arthritis (peripheral, axial - sacroiliitis, ankylosing spondylitis).
    • Skin: Erythema nodosum, Pyoderma gangrenosum.
    • Ocular: Uveitis, episcleritis.
    • Hepatobiliary: Primary Sclerosing Cholangitis (PSC; esp. UC), gallstones (CD).
    • Other: Clubbing, aphthous ulcers. Pyoderma gangrenosum lesions on back

⭐ Primary Sclerosing Cholangitis (PSC) is strongly associated with Ulcerative Colitis and carries a high risk of cholangiocarcinoma.

High‑Yield Points - ⚡ Biggest Takeaways

  • Crohn's Disease (CD): Skip lesions, transmural, granulomas, cobblestoning. Terminal ileum common. ASCA positive.
  • Ulcerative Colitis (UC): Continuous colonic, starts rectum, mucosal only, crypt abscesses, pseudopolyps. p-ANCA positive.
  • Complications: CD: fistulas, strictures. UC: toxic megacolon, ↑CRC risk.
  • EIMs: Arthritis, uveitis, erythema nodosum, pyoderma gangrenosum, PSC (UC > CD).
  • Smoking: Worsens CD; protective for UC.
  • Treatment: 5-ASA (mild UC), steroids (flares), immunomodulators, biologics.

Practice Questions: Inflammatory Bowel Disease

Test your understanding with these related questions

What is the differentiating feature between irritable bowel syndrome and inflammatory bowel disease?

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Flashcards: Inflammatory Bowel Disease

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_____ (IBD) is associated with the 'lead pipe' sign on imaging, secondary to loss of haustra

TAP TO REVEAL ANSWER

_____ (IBD) is associated with the 'lead pipe' sign on imaging, secondary to loss of haustra

Ulcerative colitis

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