Diagnostic approach to IBD

Diagnostic approach to IBD

Diagnostic approach to IBD

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Initial Workup - Spotting the Flames

  • Clinical Picture: Suspect in patients with chronic (>6 weeks) diarrhea, abdominal pain, weight loss, and/or signs of malabsorption.
  • Lab Panel:
    • CBC for anemia (microcytic) & thrombocytosis.
    • CMP for ↓albumin, electrolyte issues.
    • Inflammatory markers: ↑ESR, ↑CRP.
  • Stool Studies:
    • Rule out infectious causes (esp. C. difficile).
    • Inflammatory markers: Fecal calprotectin or lactoferrin.

⭐ Fecal calprotectin is a highly sensitive non-invasive marker of intestinal inflammation, key for differentiating IBD from IBS and justifying endoscopy.

Endoscopy & Biopsy - The Gold Standard

Crohn's vs. Ulcerative Colitis: Clinical & Endoscopic

Colonoscopy with ileoscopy is the definitive procedure. Multiple biopsies from both inflamed and normal-appearing mucosa are crucial for diagnosis and dysplasia surveillance.

  • Crohn's Disease (CD) Findings:
    • Endoscopy: Skip lesions (discontinuous), aphthous to deep linear ulcers, cobblestoning, strictures.
    • Biopsy: Transmural inflammation, lymphoid aggregates.
  • Ulcerative Colitis (UC) Findings:
    • Endoscopy: Continuous, circumferential inflammation starting from rectum; edema, friability, pseudopolyps.
    • Biopsy: Inflammation limited to mucosa/submucosa, crypt abscesses, crypt distortion.

⭐ Non-caseating granulomas on biopsy are pathognomonic for Crohn's Disease, though found in <30% of specimens.

Serology & Stool Tests - Helpful Clues

  • Serology (Antibody Tests): Not for primary diagnosis, but can provide supportive clues.

    • p-ANCA (perinuclear anti-neutrophil cytoplasmic Ab): More common in Ulcerative Colitis (~65%).
    • ASCA (Anti-Saccharomyces cerevisiae Ab): More common in Crohn's Disease (~65%).
    • 📌 Mnemonic: ASCA for Crohn's.
  • Stool Markers (Inflammatory):

    • Fecal Calprotectin & Lactoferrin: Neutrophil-derived proteins that are ↑ with intestinal inflammation.
    • Key use: Differentiating IBD from non-inflammatory etiologies (e.g., IBS).
    • Also valuable for monitoring disease activity.

⭐ Fecal calprotectin has a high negative predictive value; a normal level makes IBD very unlikely, effectively helping to rule it out in patients with chronic diarrhea.

Imaging - A Deeper Look

  • MRE/CTE (Enterography): Preferred for small bowel assessment in Crohn's.

    • Key Crohn's Findings:
      • Bowel wall thickening (>3 mm) & mural enhancement
      • Strictures, fistulas, abscesses
      • "Comb sign" (mesenteric hypervascularity)
      • "Creeping fat" (fibrofatty proliferation)
  • Barium Studies (Historical/Classic):

    • Crohn's: "String sign" of Kantor (severe terminal ileum narrowing), cobblestoning, fistulas.
    • UC: "Lead pipe" colon (loss of haustra), fine ulcerations.

Pearl: MRE is preferred over CTE to limit cumulative radiation exposure, a key consideration in young IBD patients who require serial imaging.

High-Yield Points - ⚡ Biggest Takeaways

  • Initial workup includes stool studies (calprotectin, infection), CBC, and inflammatory markers (CRP/ESR).
  • Colonoscopy with biopsy is the gold standard for diagnosis and differentiation.
  • UC features continuous, superficial colonic inflammation and is often p-ANCA positive.
  • Crohn's disease has transmural, skip lesions from mouth to anus, is ASCA positive, and shows non-caseating granulomas.
  • CT or MR enterography evaluates small bowel involvement and complications like fistulas, especially in Crohn's.
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Practice Questions: Diagnostic approach to IBD

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A 33-year-old man has a history of intermittent bloody diarrhea, tenesmus, fever, fatigue, and lower abdominal cramps for the past 2 weeks. On physical examination, he is lethargic and appears lean and pale. He has aphthous stomatitis, red congested conjunctiva, and tender swollen joints. At the doctor’s office, his pulse is 114/min, blood pressure is 102/76 mm Hg, respirations are 20/min, and his temperature is 39.4°C (102.9°F). There is vague lower abdominal tenderness and frank blood on rectal examination. Laboratory studies show: Hemoglobin 7.6 g/dL Hematocrit 33% Total leucocyte count 22,000/mm3 Stool assay for C.difficile is negative Abdominal X-ray shows no significant abnormality He is symptomatically managed and referred to a gastroenterologist, who suggests a colonoscopy and contrast (barium) study for the diagnosis. Which of the following is the most likely combination of findings in his colonoscopy and barium study?

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Flashcards: Diagnostic approach to IBD

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Extraintestinal manifestations of IBD include _____, such as erythema nodosum and pyoderma gangrenosum

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Extraintestinal manifestations of IBD include _____, such as erythema nodosum and pyoderma gangrenosum

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