Establishing the diagnosis

Investigations to establish the diagnosis of suspected Crohn's disease include:

• colonoscopy with multiple biopsy specimens is used as the first line procedure to establish the diagnosis (1): assessment of strictures, colonic polyps, allow biopsy of terminal ileum, or multiple biopsies if a barium enema was equivocal
• sigmoidoscopy and rectal biopsy
• small bowel radiology: indicated if there are symptoms suggestive of small bowel involvement - diarrhoea, pain and weight loss. Crohn's colitis should be excluded by a subsequent barium enema.
• barium enema: this is often more readily available than a colonoscopy. If positive, then small bowel radiology may be indicated to exclude other disease sites.
• blood:
  • anaemia is common - generally iron deficiency anaemia, rarely B12 or folate deficiency
  • ESR and platelet count are usually raised, albumin is usually lowered
• stool examination: Cl difficile toxin assay, pathogens
• biopsy: granulomata are characteristic
• laparotomy: often necessary to distinguish a Crohn's stricture from other causes of strictures, e.g. malignancy. Particularly relevant to the ileal form.
• small bowel capsule endoscopy (SBCE) –
  • used in patients with negative ileocolonoscopy and radiological examinations but with a high degree of clinical suspicion of Crohn’s disease
  • sensitive in detecting small bowel mucosal abnormalities
  • contraindications are - gastrointestinal obstruction, strictures or fistulas, implanted electromedical devices (pacemakers) and swallowing disorders (1)

Reference:

• (1) Van Assche G et al. The second European evidence-based consensus on the diagnosis and management of Crohn's disease: Definitions and diagnosis. Journal of Crohn's and Colitis 2010; 4:7–27