What are the recommended investigations for a patient with suspected ulcerative colitis presenting with diarrhea and abdominal pain?

Guideline-aligned answer with reasoning, red flags and references. Clinically reviewed by Dr Kola Tytler MBBS CertHE MBA MRCGP.

Posted: 16 August 2025Updated: 16 August 2025 Guideline-Aligned (High Confidence) Clinically Reviewed
Dr Kola Tytler MBBS CertHE MBA MRCGPClinical Lead • iatroX

For a patient presenting with suspected ulcerative colitis with symptoms of diarrhea and abdominal pain, the recommended investigations include:

  • Blood tests: Full blood count (FBC) to check for anaemia and inflammatory markers such as erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) to assess inflammation levels.
  • Stool tests: To exclude infections and other causes of diarrhea.
  • Endoscopic evaluation: Flexible sigmoidoscopy or colonoscopy with biopsy is essential to confirm the diagnosis and assess the extent and severity of mucosal inflammation.
  • Additional antibody testing: To exclude other conditions such as coeliac disease if clinically indicated.

These investigations help differentiate ulcerative colitis from other causes of diarrhea and abdominal pain and guide appropriate management.

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