Definition
Crohn’s disease is a chronic transmural inflammatory disorder of unknown cause affecting the alimentary tract (any part from mouth to anus). Crohn’s disease and ulcerative colitis together are referred to as idiopathic inflammatory bowel disease.
Key Points
- May present with acute, subacute or chronic manifestations.
- Perianal disease is common and may be the presenting feature.
- Increasingly seen in children of all ages.
- Immunomodulation and biological agents are the mainstay of Rx.
- Surgery is common but not curative and should be used sparingly.
- Chronic disabling disease with recurrent relapses. 10% of sufferers disabled by the disease.
Epidemiology
Male : female 1:1.6. Young adults. High incidence among Europeans and Jewish people. Family tendency to the disease.
Aetiology
- Unknown.
- Genetic link probable. Following genes may be involved: NOD2/CARD-15, IBD-3, IBD-5, IL23R, ATg16L1.
- Impaired cell-mediated immunity. Chronic inflammation from Th-1 cell activation producing IL-12, TNF-α, IFN-γ.
- Smoking doubles the risk of relapse of Crohn’s disease.
- No proven link to mycobacterial infection or measles virus hypersensitivity.
Pathology
Macroscopic
- May affect any part of the alimentary tract.
- Skip lesions in bowel (affected bowel wall and mesentery are thickened and oedematous, frequent fistulae).
- Affected bowel characteristically ‘fat wrapped’ by mesenteric fat.
- Perianal disease characterized by perianal induration (blue skin discoloration) and sepsis with fissure, sinus and fistula formation.
Histology
- Transmural inflammation in the form of lymphoid aggregates.
- Non-caseating epithelioid cell granulomas with Langhans giant cells. Regional nodes may also be involved.
Clinical Features
Acute Presentations (Uncommon)
- RIF peritonitis (like appendicitis picture).
- Generalized peritonitis (due to free perforation).
- Acute colitis: uncommon as primary presentation.
Subacute Presentations (Common)
- RIF inflammatory mass (often ± fistulae or abscesses).
- Widespread ileal inflammation: general ill health, malnutrition, anaemia, abdominal pain.
- Colitis: abdominal pain and bloody diarrhoea.
Chronic Presentations
- Strictures: intermittent colicky abdominal pains associated with eating – ‘food fear’.
- Malabsorption (due to widespread disease often with previous resections).
- Growth retardation in children (due to chronic malnutrition and chronic inflammatory response suppressing growth).
Perianal Disease
- Up to one-third of patients may have perianal disease.
- Large, oedematous, ‘blueish’ skin tags typical.
- Fissure-in-ano, fistula-in-ano, perianal sepsis.
Extraintestinal Features
- Eye: episcleritis, uveitis.
- Acute phase proteins, e.g. CRP.
- Joints: arthritis (sacroiliac joint arthritis, ankylosing spondylitis).
- Skin: erythema nodosum, pyoderma gangrenosum.
- Liver: sclerosing cholangitis, cirrhosis.
Investigations
- FBC: macrocytic anaemia, WBC raised, ESR raised.
- Acute phase proteins, e.g. CRP.
- Small bowel enema: narrowed terminal ileum, ‘string sign’ of Kantor, stricture formation, fistulae.
- Abdominal ultrasound: RIF mass, abscess formation.
- CT scan: RIF mass, abscess formation.
- Colonoscopy and intubation of terminal ileum and biospy.
- Indium-labelled white-cell scan: areas of inflammation.
- Video capsule endoscopy.
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