Crohn's disease


  • Can involve any part of the GI tract from the mouth to the anus
  • Bimodal distribution: 15-22yr, 55-60yr
  • Pathology
    • All layers of the bowel are involved
      • Reason why fistulas and abscesses are common complications
    • "Skip lesions" are common

Crohn's disease vs. ulcerative colitis

Finding Crohn's disease Ulcerative colitis
Depth of inflammation May be transmural, deep into tissues Shallow, mucosal
Distribution of disease Patchy areas of inflammation (skip lesions) Continuous area of inflammation
Terminal ileum involvement Commonly Seldom
Colon involvement Usually Always
Rectum involvement Seldom Usually (95%)
Involvement around anus Common Seldom
Stenosis Common Seldom

Clinical Features

An aphthous mouth ulcer (aphthous stomatitis) on seen with Crohn's disease.
A single lesion of erythema nodosum.

GI Symptoms

Extraintestinal Symptoms (50%)

Differential Diagnosis





  • Rule out alternate etiologies for symptoms
  • Evaluate for complications (e.g. fistulae, abscess, obstruction)
  • Labs
    • CBC
    • Chemistry
    • LFTs/lipase
    • May additionally consider:
      • ESR/CRP
      • Type and screen (if concern for significant bleeding)
      • Fecal calprotectin (sensitive indicator of intestinal inflammation, unreliable in select Crohn's patients)[1]
      • C.diff toxin
  • Consider imaging:
    • CT A/P if concern for small bowel obstruction, perforation, or toxic megacolon
      • Most useful diagnostic test in patients with acute symptoms who have known or suspected Crohn
      • Findings: bowel wall thickening, mesenteric edema, local abscess, fistulas



CT scan showing Crohn's disease in the fundus of the stomach.

Acute Flare Management

Chronic Treatment

Alterations should be discussed with GI

  • Aminosalicylates (5-ASA) - Mild-to-moderate Crohn's disease. Give with probiotics.
  • Anti-diarrheal - Use caution in patients with active inflammation as can precipitate toxic megacolon
  • Glucocorticoids - Symptomatic relief (course not altered)
    • Prednisone - 40-60mg/day with taper once remission induced
    • Methylprednisolone 20mg IV q6hr
    • Hydrocortisone 100mg q8hr
      • Do not start if any suspicion of infection (ie C. diff colitis)
      • Double edge sword: Reduction of bone density in addition to underlying disease process(decreased Ca absorption)
  • Antibiotics - Induce remission
  • Immunomodulators - Steroid-sparing agents used in fistulas and patients with surgical contraindication. Slower onset.
    • 6-Mercaptopurine 1-1.5mg/kg/day → Start at 50mg daily
    • Azathioprine 2-2.5mg/kg/day → Start at 50mg daily
    • Methotrexate IM
  • Anti-TNF - Medically resistant moderate-to-severe Crohn's disease
    • Infliximab (Remicade) 5mg/kg IV
    • Adalimumab (Humira), Natalizumab or certolizumab pegol can also be used


Inpatient Admission

Surgical Intervention

Consult EARLY if any of the following suspicions


  • Bowel obstruction
    • Due to stricture or bowel wall edema
  • Abscess
    • Can be intraperitoneal, retroperitoneal, interloop, or intramesenteric
      • More severe abdominal pain than usual
      • Fever
      • Hip or back pain and difficulty walking (retroperitoneal abscess)
  • Fistula
    • Occurs due to extension of intestinal fissure into adjacent structures
    • Suspect if changes in patient's symptoms (e.g. BM frequency, amt of pain, wt loss)
  • Perianal disease
  • Hemorrhage
    • Erosion into a bowel wall vesel
  • Toxic megacolon
    • Can be associated with massive GI bleeding

Therapy complications

See Also


  1. van Rheenen PF, Van de Vijver E, Fidler V. Faecal calprotectin for screening of patients with suspected inflammatory bowel disease: diagnostic meta-analysis. BMJ. 2010;15(341):c3369.

1. Thomas N, Wu AW. Large intestine. In: Walls RM, Hockberger RS, Gausche-Hill M, et al., eds. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 10th ed. Elsevier; 2023.