Inflammatory Bowel Disease

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.

CD vs UC Clincher - Tale of Two Guts

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.
  • 
  • 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.

⭐ 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.