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Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) describes conditions with chronic, relapsing and remitting inflammation of the gastrointestinal tract (GIT). The two most common types of IBD are: Crohn’s disease (CD) and ulcerative colitis (UC). CD can involve any part of the gastrointestinal tract, however, most commonly affects the small intestine and/or the colon whereas UC is limited to the colon (GESA, 2018). About 5-15% of patients with IBD affecting the colon have features of both conditions (Mowat et al, 2011). Where a clear distinction cannot be made, the disorder is referred to as IBD unclassified (IBD-U) (Margo et al, 2017).

Table 1-Features for differentiating between UC and CD (GESA, 2017)


IBD is a chronic disease; there is great variation in the duration of active disease and remission (characterised by complete resolution of symptoms and endoscopic mucosal healing). Disease activity is further defined as mild, moderate or severe using validated tools. In Australia, the Crohn’s Disease Activity Index (CDAI) and Harvey-Bradshaw Index (HBI) are the most commonly used tools to assess CD activity and either the Simple Colitis Clinical Activity Index (SCCAI) or the partial Mayo Clinical Index is used for assessing UC disease activity.


Gastroenterological Society of Australia (GESA). Inflammatory Bowel Disease Clinical Update 2018 4th Edition. Accessed:

Mowat C, Cole A, Windsor A, et al. Guidelines for the management of inflammatory bowel disease in adults. Gut. 2011;60(5):571–607.

Magro F, Gionchetti P, Eliakim R, et al. Third European Evidence-based Consensus on Diagnosis and Management of Ulcerative Colitis. Part 1: Definitions, Diagnosis, Extra-intestinal Manifestations, Pregnancy, Cancer Surveillance, Surgery, and Ileo-anal Pouch Disorders. Journal of Crohn's and Colitis 2017;11(6):649–70