Table 1.

Differential diagnosis of inflammatory bowel disease (IBD; modified from [1, 4, 6])

Disease	Clinical characteristics	Distinguishing findings
Infectious gastroenteritis/colitis	Acute onset of diarrhoea with possible blood, fever, dysentery	Recent use of antibiotics, positive stool samples for pathogen agents (e.g., Clostridium difficile), pseudomembranes on endoscopy with Clostridium difficile, positive stool studies, rapid resolution with appropriate antibiotic therapy
NSAID-induced colitis	Diarrhoea with possible blood, abdominal pain, iron deficiency anaemia, obstruction, perforation	History of chronic NSAIDs use, diaphragm-like small bowel stricture, isolated lesions, any part of the intestine may be affected, exacerbate existing ulcerative colitis (UC) or Crohn's disease (CD)
Ischaemic colitis	Acute onset of abdominal pain followed by bloody diarrhoea, association with food intake	Segmental area of injury, rectal sparing, typical sigmoid/left sided colitis, rectum sparing, abrupt transition between normal and affected mucosa, possible concomitant cardiovascular disease
Segmental colitis associated with diverticulosis	Bloody stools, diarrhoea, abdominal pain	History of diverticular disease, local inflammation in and around diverticulum only at endoscopy, rectum and proximal colon spared
Radiation colitis	Bloody diarrhoea, abdominal pain, urgency, tenesmus, symptoms occur weeks to years after abdominal/pelvic radiation	History of abdominal or pelvic radiation, histological fibrosis and capillary telangiectasia (i.e., different findings from IBD)
Microscopic colitis	Non-bloody diarrhoea, predominant in females	No anatomical abnormalities visible at endoscopy, histologically different from IBD
Diversion colitis	Occurs in surgically diverted bowel loop, most asymptomatic but can haveabdominal pain and bloody/mucous discharge	Histologically, prominent lymphoid hyperplasia
Solitary rectal ulcer syndrome	Bloody diarrhoea with straining, rectal bleeding, straining, pelvic fullness	History of constipation, histologically thickened mucosal layer and crypt architectural distortion, smooth muscle and collagen replace lamina propria (i.e., different findings from IBD)

NSAID, non-steroidal anti-inflammatory drugs.