see also:

• inflammatory bowel disease (IBD)
• emedicine

• 1st described by Crohn, Ginzberg, and Oppenheimerf in 1932.
• it is thought that interplay between the gut’s bacteria and immune system responses are a critical step in developing Crohn’s Disease
  • the presence of Lachnospiraceae flagellin antibodies long before any symptoms appear suggests that this immune reaction may contribute to triggering the onset of the disease, rather than being a consequence of it and can predict some Crohn's disease in first degree relatives well before symptomatic stage ¹⁾

• 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

• 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

• 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)

• 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

• raised C reactive protein (CRP) is an indicator of disease activity
• 20% have raised liver function tests (LFTs)
  • 60% of these patients have mild, transient raised LFTs and many are related to drug-induced cholestasis
  • most of those with persistent changes were due to fatty liver disease and had a cholestatic picture ²⁾
• 10-40% are ANCA positive (cw 50-85% of patients with ulcerative colitis and 50-85% of those with primary sclerosing cholangitis (PCC), a chronic cholestatic liver disease that is strongly associated with IBD) ³⁾
• persistently high AP levels are suggestive of primary sclerosing cholangitis / primary biliary cirrhosis

• ulcerative colitis
• 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

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

• 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

• 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