Differential diagnosis

The differential diagnosis of Crohn's disease includes:

• ulcerative colitis. In 10 to 20% of cases the two diseases cannot be differentiated. Distinguishing features include rectal involvement and bloody diarrhoea in UC, continuous disease pathology, but no strictures or fistulae. In UC there is a low plasma IL-6 in the active disease, and there is a stronger association with non-smokers. Also, UC patients are more often p-ANCA positive.
• irritable bowel syndrome. This has no radiological abnormalities or weight loss.
• gastrointestinal malignancy. The most important cancers here are lymphoma, right colonic cancer and small bowel cancer. These patients might be expected to have night sweats and anaemia. Radiologically there may be a mass and metastases.
• ileal tuberculosis. This should be investigated for with a stool culture, and might be suspected in the immigrant population. Pathologically, after laparoscopic biopsy there will be caseating granulomas and mesenteric tubercules.
• anorexia nervosa
• coeliac disease - this will cause a malabsorptive picture
• chronic infection with Giardia, Yersinia and Campylobacter
• amyloidosis
• Behcet's disease
• Whipple's disease
• diverticulitis
• ischaemic colitis
• microscopic colitis – there is watery diarrhoea often associated with NSAID’s and other drugs (1)

Reference:

• (1) Cummings JR, Keshav S, Travis SP. Medical management of Crohn's disease. BMJ. 2008;336(7652):1062-6