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Crohn’s Disease

  • A form of inflammatory bowel disease (IBD) that can affect any part of the GIT (mouth to anus), especially the terminal ileum

Epidemiology

  • Most common in UK and Scandinavian countries
  • More common in Jewish people
  • Bimodal age distribution – 15-30 and 50-80 years old

Etiology

  • Etiology is largely unknown but there are familial, infectious and environmental theories
  • Infective – dysregulated response to M. tuberculosis
  • Genetic – associated with the NOD2/CARD15 gene on chromosome 16
  • Immunologic
    • Abnormal host response to dietary antigens
    • Defective mucosal barrier – increases exposure to antigens
  • Environmental – smoking

Pathology

  • Can affect any part of GIT
  • Multiple areas may be involved with intervening areas of normal bowel – skip lesions
  • Mesentery is thickened
  • Mesenteric fat creeps along the sides of the bowel wall toward the anti-mesenteric border – fat wrapping
  • Involves all layers of the bowel wall – transmural
    • Whereas ulcerative colitis involves only the mucosa and submucosa
  • Ulcerations range from short, shallow, aphthous ulcers to deep fissuring ulcers
    • Fissuring of mucosa and the submucosal edema give the bowel cobblestone appearance with formation of pseudopolyps
  • If ulcers fully penetrate it can lead to fistula formation
  • Bowel wall can thicken with fibrosis, causing stricture formation
  • Peri-anal Crohn’s disease can lead to peri-anal fistulas and abscesses

Histology

  • Lymphocytic infiltration in all layers of bowel
  • Non-caseating granulomas

Clinical features

  • Classic triad – abdominal pain, diarrhoea, weight loss
    • Usually a slow, insidious presentation
  • Others – anorexia, fever, recurring oral aphthous ulcers
  • Peri-anal disease – fissure, fistula, abscess
  • Extra-intestinal manifestations
    • Skin – erythema nodosum, pyoderma gangrenosum
    • Eyes – iritis, uveitis
    • Joints – arthritis, ankylosing spondylitis
    • Blood – anaemia, thrombocytosis, DVT
    • Sclerosing cholangitis
    • Nephrotic syndrome
    • Pancreatitis
    • Amyloidosis

Investigations

  • Serology – ASCA (+) and pANCA (-) is highly suggestive of Crohn’s disease
    • Inverse pattern is highly suggestive of ulcerative colitis – ASCA (-) and pANCA (+)
  • Barium small bowel follow through – strictures
  • Colonoscopy – shows cobblestone appearance
  • Biopsy – to distinguish from ulcerative colitis
  • CT, MRI

Treatment

Lifestyle changes

  • Smoking cessation
  • High fibre diet
  • A food diary – to help identify foods that may trigger flare ups

Medical

  • Corticosteroids – budesonide, methylprednisolone, prednisone
    • To induce remission in the initial phase of the disease
  • Antibiotics – metronidazole
  • Aminosalicylates – sulfasalazine, mesalamine
    • For maintenance
    • However they are more effect in ulcerative colitis
  • Azathioprine – for maintenance
  • Methotrexate
  • Monoclonal antibody – infliximab (anti-TNF)

Surgery

  • Surgery is not a definitive cure as the disease eventually recurs
  • Indications for surgery
    • Intractability
    • Intestinal obstruction
    • Fistulas
    • Toxic megacolon
    • Massive bleeding
  • Surgeries
    • Stricuroplasty
    • Ileocecal resection followed by anastomosis between the ileum and ascending colon
    • Surgery for peri-anal diseases – i.e. for fissures, abscess and fistula
    • Segmental colon resection – when inflammation is limited to a specific segment of colon
    • Total proctocolectomy – removal of colon, rectum and anus
    • Total abdominal colectomy – removal of colon, but sparing the rectum and anus
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