351.1 🎓 醫孞生版

351.1.0.1 📌 䞀頁重點

351.1.0.1.1 Epidemiology
  • ~ 0.5% prevalence in Western countries
  • Increasing in Asia (Taiwan included)
  • Bimodal peak: 15-30 yo + 50-80 yo
  • Slight female predominance in CD
  • Genetic + environmental (smoking + UC inversely, CD positively; appendectomy + UC inversely)
351.1.0.1.2 Comparison CD vs UC
Feature Crohn’s Disease Ulcerative Colitis
Location Mouth to anus, ileum + colon most Colorectum only, starts rectum continuous
Pattern Skip lesions Continuous
Inflammation Transmural Mucosal
Granulomas Yes (non-caseating) No
Fistulas Yes No
Strictures Yes Rare
Smoking Worsens Protective
Surgery Not curative Colectomy curative
pANCA 10% 60-70%
ASCA 60% 10%
Bloody diarrhea Less common Hallmark
351.1.0.1.3 Crohn’s Disease (CD)

351.1.1 Distribution

  • Ileocolic (50%)
  • Ileal only (30%)
  • Colonic only (20%)
  • Perianal disease common
  • Upper GI involvement less

351.1.2 Symptoms

  • Crampy abdominal pain
  • Diarrhea (variable; ± blood)
  • Weight loss + fatigue
  • Perianal disease (fistulas, abscesses)
  • Strictures → obstruction
  • Fistulas (enteroenteric, enterovesical, enterocutaneous)
  • Abscesses
  • Anal disease (fissures, skin tags)

351.1.3 Pathology

  • Transmural granulomatous inflammation
  • Cobblestone appearance
  • Aphthous ulcers → linear deep ulcers
  • Granulomas (non-caseating)
  • Fibrosis → strictures
351.1.3.0.1 Ulcerative Colitis (UC)

351.1.4 Distribution

  • Always involves rectum
  • Extends proximally continuously
  • Categories:
    • Proctitis: rectum only (30-50%)
    • Left-sided colitis: to splenic flexure (20-30%)
    • Extensive / pancolitis: beyond splenic flexure (20-30%)

351.1.5 Symptoms

  • Bloody diarrhea (hallmark)
  • Tenesmus
  • Urgency
  • Lower abdominal cramps
  • Weight loss (severe)
  • Fever (severe / fulminant)
  • Toxic megacolon (severe complication)

351.1.6 Pathology

  • Mucosal + submucosal inflammation
  • Pseudopolyps (regenerative)
  • Crypt abscesses
  • No granulomas (key feature)
351.1.6.0.1 Extraintestinal Manifestations

Joint (most common): - Type 1 (oligoarticular, peripheral, parallels disease) - Type 2 (polyarticular, peripheral, independent of disease) - Ankylosing spondylitis (independent) - Sacroiliitis

Skin: - Erythema nodosum (mostly UC) - Pyoderma gangrenosum - Sweet syndrome

Eye: - Uveitis - Episcleritis - Scleritis

Hepatobiliary: - Primary sclerosing cholangitis (PSC) — strongly UC-associated - Cholelithiasis - Steatosis

Renal: - Calcium oxalate stones (CD) - Amyloidosis

Hematologic: - Anemia (chronic disease, iron deficiency, blood loss) - Thrombocytosis (active) - Hypercoagulability

Other: - Aphthous stomatitis - Nutritional deficiencies (B12 in terminal ileal CD) - Osteoporosis (steroids, malabsorption) - Growth failure (pediatric)

351.1.6.0.2 Diagnosis

351.1.7 Clinical + Labs

  • Symptoms + extraintestinal
  • CBC (anemia, leukocytosis, thrombocytosis)
  • ESR, CRP (active disease)
  • Albumin (chronic disease)
  • LFTs
  • TSH, B12, iron studies

351.1.8 Stool Studies

  • C. diff (rule out, especially flare)
  • Bacterial culture
  • O&P
  • Fecal calprotectin (sensitivity for IBD activity)

351.1.9 Endoscopy

  • Colonoscopy + ileal intubation + biopsy = gold standard
  • Distribution + severity
  • Differentiate CD vs UC
  • Rule out infection
  • Biopsy multiple sites

351.1.10 Imaging

  • MR enterography (MRE) — preferred for CD (small bowel)
  • CT enterography (alternative)
  • US (emerging)
  • CT for complications

351.1.11 Serology

  • pANCA (UC > CD)
  • ASCA (CD > UC)
  • Not routine; supplementary
351.1.11.0.1 Treatment

351.1.12 Goals

  • Induce remission
  • Maintain remission
  • Mucosal healing
  • Prevent complications
  • Improve QoL

351.1.13 Treatment by Severity

351.1.13.1 Mild

5-ASA Agents (mainstay for UC; less in CD): - Mesalamine (Pentasa, Asacol, Lialda) - Sulfasalazine - Topical (suppositories, enemas) for distal UC - Oral + topical combination for left-sided

Topical Corticosteroids: - Budesonide (less systemic effect) - For mild active disease

351.1.13.2 Moderate-Severe

Systemic Corticosteroids: - Prednisone, methylprednisolone IV - For induction - Not for maintenance (side effects) - Taper over weeks-months

Immunomodulators: - Thiopurines (azathioprine, 6-mercaptopurine) — TPMT testing pre-treatment - Methotrexate (CD only mostly) - For maintenance

Biologics:

Anti-TNF: - Infliximab (Remicade) — IV, every 8 weeks - Adalimumab (Humira) — SC, every 2 weeks - Certolizumab pegol (Cimzia) — SC, every 4 weeks - Golimumab (Simponi) — SC, every 4 weeks (UC only) - For moderate-severe induction + maintenance - Fistulizing CD particularly responsive (infliximab) - TB + hepatitis B screening pre-treatment

Anti-Integrin: - Vedolizumab (Entyvio) — gut-selective; less systemic IS - IV every 4-8 weeks - For UC + CD

Anti-IL-12/IL-23: - Ustekinumab (Stelara) — IV induction → SC maintenance - Both UC + CD - Efficacy + safety profile

Selective Anti-IL-23: - Risankizumab (Skyrizi) — CD (FDA 2022); + UC (FDA 2024) - Mirikizumab (Omvoh) — UC (FDA 2023) - Guselkumab (Tremfya) — emerging - More selective + potentially safer

JAK Inhibitors: - Tofacitinib (Xeljanz) — UC (FDA approved) - Upadacitinib (Rinvoq) — UC + CD (FDA approved) - Oral - Black box: cardiovascular + thrombotic events (especially in ≥ 50 + RA + smokers)

S1P Modulators: - Ozanimod (Zeposia) — UC (FDA 2021) - Etrasimod (Velsipity) — UC (FDA 2023) - Oral - Sphingosine-1-phosphate receptor modulators

351.1.14 Treatment Strategies

Step-Up Therapy: - 5-ASA → corticosteroid → immunomodulator → biologic - Conservative - Used for mild-moderate

Top-Down Therapy: - Early biologic for moderate-severe - ↓ Complications - ↓ Surgery - More evidence-based for moderate-severe

Treat-to-Target: - Mucosal healing - Biomarker-guided (CRP, calprotectin) - Periodic endoscopic + imaging

351.1.15 Specific Situations

Toxic Megacolon (Severe UC): - IV corticosteroids - Antibiotics - Cyclosporine or infliximab rescue - Colectomy if refractory (24-72 hr)

Perianal Fistulizing CD: - Infliximab (best evidence) + drainage / setons - Combination biologic + immunomodulator - Surgery for refractory

Pregnancy: - Continue biologics through pregnancy (especially TNFi) - Methotrexate contraindicated - Thiopurines acceptable - Plan with IBD specialist

351.1.16 Surgery

Crohn’s: - Not curative - For complications: strictures, fistulas, perforation, malignancy - Limited resection - Endoscopic balloon dilation for strictures

UC: - Total proctocolectomy curative - Ileal pouch-anal anastomosis (IPAA / J-pouch) preferred - Indications: refractory, dysplasia, cancer, fulminant - Pouchitis risk (treat with metronidazole, ciprofloxacin)

351.1.16.0.1 Colorectal Cancer Surveillance

351.1.17 Risk

  • ↑ With duration + extent + PSC
  • UC > CD (colonic)
  • Greater for pancolitis ≥ 10 years

351.1.18 Surveillance

  • Begin 8-10 years after disease onset (UC)
  • Earlier with PSC
  • Colonoscopy every 1-2 years
  • Multiple biopsies (random + chromoendoscopy)
  • Confirmed dysplasia → consider colectomy
351.1.18.0.1 Monitoring + Long-Term
  • Periodic colonoscopy + lab
  • Calprotectin + imaging for relapse
  • Vaccinations (avoid live during biologic)
  • Bone density (steroids)
  • Mental health
  • Pregnancy planning

351.1.18.1 🩺 床邊速查

  • CD: transmural, skip lesions, any GI, fistula + stricture; smoking worsens
  • UC: mucosal, continuous from rectum, colorectum only; bloody diarrhea hallmark; smoking protective
  • Diagnosis: colonoscopy + biopsy + fecal calprotectin; MRE for CD
  • Biologics era: TNF inhibitors (infliximab) + anti-integrin (vedolizumab) + anti-IL-12/23 (ustekinumab) + anti-IL-23 selective (risankizumab, mirikizumab) + JAK inhibitors + S1P modulators
  • Top-down: early biologic for moderate-severe; reduces complications
  • UC colectomy curative
  • CRC surveillance every 1-2 yr after 8-10 yr disease
  • Extraintestinal: joints (#1), skin (EN, PG), eye (uveitis), PSC (UC)