Which initial investigations should be conducted for a patient suspected of having Inflammatory Bowel Disease?

Initial investigations for a patient suspected of having inflammatory bowel disease (IBD) should include:

• Blood tests: full blood count to detect anaemia, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) to assess inflammation, liver function tests including albumin, calcium, vitamin B12, red blood cell folate, iron studies (ferritin), and thyroid function tests ³.
• Serological testing for coeliac disease using immunoglobulin A (IgA) and IgA tissue transglutaminase (tTG) or endomysial antibody (EMA) to exclude coeliac disease as a cause of symptoms ³.
• Faecal calprotectin testing to help differentiate IBD from irritable bowel syndrome in people under 40 years if cancer is not suspected; however, it should not be used if there is new onset rectal bleeding or bloody diarrhoea or if cancer needs to be ruled out ³.
• Stool samples for routine microbiology and examination for ova, cysts, and parasites if infection or travel history suggests an infectious cause ³.
• Colonoscopy with multiple intestinal biopsies for histological confirmation and classification of disease extent and severity, which is essential for diagnosis of both Crohn's disease and ulcerative colitis ¹,².
• Upper gastrointestinal endoscopy in children and young people, and in adults with upper GI symptoms, to differentiate Crohn's disease from ulcerative colitis ¹,².
• Imaging studies such as magnetic resonance enterography (MRE) or MRI of the small bowel, small bowel ultrasound, or capsule endoscopy may be needed if endoscopy and conventional imaging are inconclusive ¹,².
• Additional imaging like pelvic MRI for suspected perianal disease, abdominal ultrasound, CT scans, and plain abdominal X-rays may be used to assess complications and disease extent ¹,².