Crohn’s Disease

Epidemiology (1)

  • Incidence: 1.3 to 5.3 per 100,000 individuals
  • Bimodal age distribution: 1st peak: Ages 15-25, 2nd peak: Ages 50-80


  • Diarrhea +/- blood
  • Colicky abdominal pain
  • Urgency, tenesmus (constant feeling of needing to pass stools despite emptiness)
  • Systemic symptoms (fever, fatigue, weight loss)


  • Rule out other diseases
    • Amebiasis (travel history)
    • C. diff (prior antibiotic use, C. diff toxin screen)
    • Proctitis (sexual history)
    • Colonic ischemia (atherosclerotic disease, CTA),
    • Radiation/NSAID colitis (history)
    • CMV colitis (history of immunosuppression)
    • Salmonella/shigella/campylobacter/yersinia (routine stool cultures)
  • Laboratory findings
    • Anemia
    • ESR, CRP elevations
    • Fecal calprotectin (+): This is a protein found largely in neutrophils, its presence in the stool is sensitive for Inflammatory Bowel Disease (but not Crohn’s Disease in particular). This test also lacks specificity. (2)
    • Low Iron, Vitamin D, or Vitamin B12 (due to poor absorption)
  • Colonoscopy
    • Findings: “Cobblestone” appearance of the mucosa. Lesions may be discontinuous, or “skip”, instead of being continuous as they are seen in Ulcerative Colitis
  • Biopsy
    • Transmural inflammation
    • Non-caseating granulomas in 13-36% of cases (3)


  • Mild-moderate Disease (Superficial ulcers, limited extent of disease)
    • Remission:
      • Budesonide (high first-pass metabolism in the liver limits systemic side effects)
      • PO glucocorticoids (alternatively, sulfasalazine)
        • Attempt to taper off. If unable, consider moving to management for moderate-severe disease
    • Maintenance:
      • If remission achieved by glucocorticoid, taper off, observe with repeat colonoscopy
      • If remission required treatment with below therapies, continue those as maintenance therapy
  • Moderate-severe Disease (Deep ulcers, diffuse disease, perianal involvement)
    • TNF-α inhibitors (i.e. infliximab, adalimumab, and certolizumab)
      • Need tuberculosis and HBV screening prior to initiation of therapy
    • Immunomodulator [Thiopurines (i.e. azathioprine, or its metabolite, 6-mercaptopurine), or methotrexate]
      • Check Thiopurine Methyltransferase (TPMT) activity before initiating thiopurines. Decreased activity may lead to an increased risk of thiopurine-induced myelosuppression (4)
      • Attempt discontinuation within 1-2 years post-remission if colonoscopy confirms subsided inflammation. May continue TNF-α inhibitor
    • For remission/induction, may use either of the above options in isolation or in combination. May also use glucocorticoids initially as a bridge to these other therapies
  • American Gastroenterological Association (AGA) recommends a screening colonoscopy at MAXIMUM 8 years after diagnosis. After that, next screening colonoscopy as early as 1-2 years later if the disease is diffuse or if the left colon is involved (5)


  • Intestinal
    • Colon cancer associated with Crohn’s Disease with >1/3 colonic involvement
    • Bleeding/Anemia
    • Fistulas (Enteroenteric, enterovesicular, enterovaginal, enterocutaneous)
    • Abscess
    • Malabsorption -> Mineral and vitamin deficiencies (especially fat-soluble vitamins)
  • Extraintestinal
    • Arthritis
    • Ankylosing Spondylitis
    • Erythema nodosum
    • Pyoderma gangrenosum (though much more frequently associated with Ulcerative Colitis)
    • Primary Sclerosing Cholangitis (though much more frequently associated with Ulcerative Colitis)
    • Uveitis


  1. AL;, S. (n.d.). Epidemiology of Crohn’s Disease. Retrieved January 16, 2021, from
  2. Pathirana, W., Chubb, S., Gillett, M., & Vasikaran, S. (2018, August). Faecal Calprotectin. Retrieved December 28, 2020, from
  3. Park JB;Yang SK;Myung SJ;Byeon JS;Lee YJ;Lee GH;Jung HY;Hong WS;Kim JH;Min YI;. (n.d.). [Clinical characteristics at diagnosis and course of Korean patients with Crohn’s disease]. Retrieved January 16, 2021, from
  4. Nguyen, C., Mendes, M., & Ma, J. (2011, May 15). Thiopurine methyltransferase (TPMT) genotyping to predict myelosuppression risk. Retrieved January 16, 2021, from
  5. Lee, J., & Lee, K. (2016, July). Endoscopic Diagnosis and Differentiation of Inflammatory Bowel Disease. Retrieved January 16, 2021, from

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