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Crohn's disease


  • 1st described by Crohn, Ginzberg, and Oppenheimerf in 1932.


  • rare, but common in exams as young patients who speak English readily available!
  • onset usually between 15-40yrs age
  • the age of onset has a bimodal distribution:
    • first peak occurs between the ages of 15-30 years
    • second peak occurs between the ages of 60-80 years
  • M=F
  • 3-8x risk in Jewish than non-Jews
  • incidence in USA has been doubling every 10yrs for past 30yrs
  • in both Europe and North America, higher incidence rates have been characterized in more northern latitudes
  • prevalence in US ~7 cases per 100,000 population
  • incidence rates in Europe range from 0.7 to 9.8 cases per 100,000 persons


  • chronic granulomatous inflammation extending through ALL layers of bowel wall & involving LNs
  • it appears the yeast fungus Debaryomyces hansenii may have a role in impairing healing of gut ulcers in patients with Crohns disease by increasing the levels of a cytokine called CCL5 (chemokine ligand 5)
  • important distinguishing features from ulcerative colitis:
    • involvement of all layers not just mucosa & submucosa
    • skip lesions (lips to anus) rather than continuous lesions
    • rectal involvement NOT common BUT anorectal complications such as fistulae/abscesses are common
    • characteristic small bowel involvement

clinical features

  • being rare, initial presentation usually as a “mask” for other conditions (but features of > 1 mask may be present):
    • terminal ileitis presenting as RIF “appendiceal” mass
      • chronic diarrhoea, abdo. cramps, fever, anorexia, weight loss
    • left colitis presenting with pain and PR bleeding
    • anorectal involvement presenting as perianal suppuration (~50% of presentations):
      • 1st perianal abscess usually just incised and drained
      • 2nd recurrence, one excludes diabetes
      • 3rd recurrence, one needs to exclude Crohn's
    • regional (segmental) colitis presenting as subacute bowel obstruction
    • extragastrointestinal presentations (each occur in 10% of pts) (rarest presentation):
      • iritis
      • episcleritis
      • erythema nodosum
      • arthritis - eg. monoarticular, sacroiliitis or ankylosing spondylitis
      • aphthous ulcers

other complications of Crohns

  • gallstones are found in 35-60%
  • malabsorption ⇒ diarrhoea
  • bowel strictures
  • fistulae ⇒ UTI, etc
  • 2-3% develop toxic megacolon
  • risk of large & small bowel cancer in prolonged illness (15-20yrs)
  • lymphoma of colon may occur
  • drug Rx related:
    • Cushing's syndrome, adrenal suppression, immunocompromise, etc from steroids
    • neuropathy (long term metronidazole)
    • nephropathy (cyclosporine)
    • bone marrow suppression (azathioprine)

diagnosis of Crohn's disease:

confirmed by:

  • sigmoidoscopy
  • biopsy of perianal lesions/abscesses, rectum or other granulomatous lesions
  • bowel contrast radiology:
    • skip lesions
    • non-involvement of rectum
    • strictures
    • 'rose thorn' ulcers
    • 'cobblestone' mucosal surfaces
    • associated carcinoma

other possible findings

differential diagnosis:

younger patients:

  • invasive infectious enteritis (eg. Campylobacter, Shigella, C difficile)
  • terminal ileitis
    • 50-80% are due to Yersinia enterocolitis which may also have extraGIT manifestations:
      • erythema nodosum, monoarticular arthritis BUT no perianal or skip lesions

elderly patients:

  • infectious colitis - esp. enteropathogenic E.coli 0157:H7 in nursing home pts eating beef

general Mx of Crohn's disease:

  • medical Rx is similar to UC but less effective (don't use to delay effective Sx for fistulae, etc):
    • prednisolone 20-30mg/day orally provides symptom control but doesnt alter prognosis
    • hydrocortisone acetate foam enemas i (125mg) 12-24h PR for 1-2wks then alternate days if rectal disease
    • metronidazole 400mg bd o may help non-responders with perianal/colonic disease
      • avoid in pregnancy
      • courses should be < 3months to avoid neuropathies
    • azathioprine (Imuran) 2mg/kg/d o may allow withdrawal of steroid Rx in pts with chronic symptoms
      • avoid in pregnancy
    • sulphasalazine may be tried, but no help in ileal disease & has no role in maintenance Rx
    • cholestyramine 4-8g tds o may help if bile salt malabsorption causes diarrhoea
    • cyclosporin 2.5-4mg/kg bd o for 3mths may help without inducing too much nephropathy
  • in active disease:
    • food intolerance (eg. cereals, milk, yeasts) may be present, so elemental diets may be as good as prednisolone, with re-introduction of foods one at a time maintains improvement without being boring
    • if steatorrhoea, then give low fat diet
    • if lactose intolerant, then lactose free diet
    • only consider TPN if enteral route cannot be used
  • surgery:
    • surgery is never curative, unlike in UC
    • bowel resections
    • stricture relief
    • aim to control symptoms

ED Mx of exacerbations of Crohn's disease

  • exacerbations usually present as increased abdominal pain, anorexia, nausea and, often increased frequency of bowel actions
  • iv fluids
  • take bloods for FBE, U&E, CRP, ESR and other Ix (eg. HCG, LFT's) as indicated by clinical assessment - don't forget the abdominal pain could be unrelated to the Crohn's disease and thus consider other causes of abdominal pain as well as potential complications of Crohn's as outlined above.
  • discuss with gastroenterology unit
  • usually require admission and iv hydrocortisone 100mg qid in addition to usual Crohn's Rx
crohns.txt · Last modified: 2022/06/04 01:18 by gary1

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