What investigations are recommended for suspected Inflammatory Bowel Disease (IBD)?

Investigations for Suspected Inflammatory Bowel Disease (IBD)

The diagnosis of IBD requires a combination of clinical evaluation, biochemical testing, stool studies, endoscopic examination with biopsies, and appropriate imaging studies, as no single reference standard exists. 1

Initial Clinical Assessment

• Detailed history should include:

  • Stool frequency and consistency
  • Presence of urgency and rectal bleeding
  • Abdominal pain characteristics
  • Systemic symptoms (malaise, fever, weight loss)
  • Extraintestinal manifestations (joint, skin, eye)
  • Recent travel history
  • Medication use
  • Smoking status
  • Family history of IBD 1

• Physical examination should assess:

  • General wellbeing
  • Vital signs (pulse, blood pressure, temperature)
  • Signs of anemia or fluid depletion
  • Weight loss
  • Abdominal tenderness or distension
  • Palpable abdominal masses
  • Perianal examination for fistulae or abscesses 1

Laboratory Investigations

Essential Blood Tests

• Full blood count (FBC) to assess for anemia and inflammation
• Urea and electrolytes (U&Es)
• Liver function tests
• Inflammatory markers:
  • C-reactive protein (CRP) - more sensitive for acute inflammation
  • Erythrocyte sedimentation rate (ESR) - better for chronic inflammation 1, 2
• Iron studies (ferritin, transferrin saturation) 1
  • Ferritin <30 μg/L indicates iron deficiency in patients without active inflammation
  • Ferritin up to 100 μg/L may still indicate iron deficiency in the presence of inflammation 1

Stool Tests

• Microbiological testing for infectious diarrhea, including:
  • Clostridium difficile toxin
  • Common bacterial pathogens
  • Ova, cysts, and parasites (particularly in those with travel history) 1
• Fecal calprotectin - values >150 μg/g suggest active intestinal inflammation 2

Endoscopic Evaluation

Sigmoidoscopy

• For patients presenting with diarrhea, rigid sigmoidoscopy should be performed unless flexible sigmoidoscopy is planned 1
• In cases of acute severe colitis, sigmoidoscopy may be sufficient to establish diagnosis 1
• Rectal biopsy should be taken even if no macroscopic changes are present 1

Colonoscopy

• Ileocolonoscopy with biopsies is the cornerstone diagnostic test for IBD 1
• For mild to moderate disease, complete colonoscopy is preferable to assess disease extent 1
• For moderate to severe disease, flexible sigmoidoscopy is safer due to increased perforation risk 1
• Terminal ileal intubation and biopsy is essential to document examination extent and detect microscopic evidence of Crohn's disease 1
• Biopsies should be taken from both inflamed and uninflamed segments 1

Endoscopic Features

• Ulcerative colitis: Continuous and confluent colonic inflammation with clear demarcation and rectal involvement 1
• Crohn's disease: Discontinuous lesions, strictures, fistulae, and perianal involvement 1

Imaging Studies

Initial Imaging

• Abdominal radiography is essential in suspected severe IBD to:
  • Exclude colonic dilatation
  • Assess disease extent in UC
  • Identify proximal constipation
  • Detect mass in right iliac fossa or small bowel dilatation in CD 1

Additional Imaging

• Small bowel radiology (follow-through or small bowel enema) for suspected Crohn's disease 1
• Ultrasound can identify thickened small bowel loops and detect abscesses or free peritoneal fluid 1
• CT and MRI, especially of the perineum, help evaluate disease activity and complications 1
• MRI enterography is preferred over CT to reduce radiation exposure in young patients 3

Disease Extent Assessment

• After confirming IBD diagnosis, disease extent should be defined as it determines therapy approach 1
• For UC, extent is defined as the proximal margin of macroscopic inflammation 1
• For CD, both small bowel and colon should be assessed 1

Histopathological Examination

• Pathological examination should attempt to define IBD type
• Mention other co-existent diagnoses or complications
• Report presence or absence of dysplasia 1

Common Pitfalls to Avoid

• Failing to exclude infectious causes before confirming IBD diagnosis
• Relying solely on serological markers (pANCA, ASCAs) which have limited accuracy
• Overlooking the need for both endoscopic and histological assessment
• Deferring necessary investigations in moderate to severe disease
• Neglecting to assess disease extent, which impacts treatment decisions and prognosis

By following this comprehensive diagnostic approach, clinicians can accurately diagnose IBD, determine disease extent, and guide appropriate treatment decisions to improve patient outcomes.