Crohn’s Disease

Definition: Crohn’s Disease is a chronic, relapsing and remitting inflammatory disease of the gastrointestinal tract, affecting any site from mouth to anus. The disease is characterised by segmental transmural inflammation, or ‘skip lesions’. Patients experience abdominal pain, cramping and diarrhoea.
Aetiology: unknown
Pathogenesis: transmural inflammation; enlargement of submucosal lymphoid follicles; obstructive lymphoedema; transverse and longitudinal ulceration of mucosa overlying lymphoid follicles (cobblestoning). End stage is fibrostenosing stricture.
Extraintestinal manifestations: skin (erythema nodosum, pyoderma gangrenosum); joints (arthritis, ankylosing spondylitis, sacroiliitis); eyes (episcleritis, iritis, uveitis); liver and biliary system (pericholangitis, sclerosing cholangitis, autoimmune hepatitis, cirrhosis).
Radiology: thickened folds (oedema); string sign (tubular narrowing due to spasm or stricture depending on chronicity); mucosal ulcers (apthous ulcers or deeper transmural ulcers); sinus tracts and fistulae; inflammation of surrounding mesentery (creeping fat) with possible abscess formation; partial obstruction (bowel wall oedema and lumenal narrowing or scarring causing fibrostenotic strictures).
References: Dähnert W. Radiology Review Manual, 5th edition, Lippincott, Williams & Wilkins, 2003. Weissleder et al. Primer of Diagnostic Imaging, 3rd edition, Mosby, 2002.
Credit: Dr Marina-Portia Anthony
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