What is the recommended workup for a patient presenting with chronic bloody diarrhea?

Workup of Chronic Bloody Diarrhea

Colonoscopy with biopsies of right and left colon is the essential first-line investigation for chronic bloody diarrhea to exclude colorectal cancer and inflammatory bowel disease. 1

Initial Assessment

History Focus Points

• Duration and frequency of symptoms
• Presence of blood (visible or occult)
• Associated symptoms (abdominal pain, weight loss, fever)
• Medication use (antibiotics, NSAIDs)
• Travel history
• Family history of colorectal cancer or inflammatory bowel disease

First-line Investigations

1. Blood tests:

   • Complete blood count
   • C-reactive protein/ESR
   • Electrolytes and liver function tests
   • Iron studies
   • Vitamin B12 and folate
   • Thyroid function tests
   • Celiac serology (anti-tissue transglutaminase IgA and total IgA) 1, 2

2. Stool tests:

   • Fecal calprotectin (to detect inflammation)
   • Fecal immunochemical test (for occult blood)
   • Stool culture and microscopy (to exclude infection)
   • Clostridium difficile testing (especially if recent antibiotic use) 1, 3

Endoscopic Evaluation

Colonoscopy

• Essential for all patients with chronic bloody diarrhea regardless of age 1
• Must include biopsies of right and left colon (not just rectum) even if mucosa appears normal 1, 4
• Terminal ileal intubation recommended when clinically indicated 1

Diagnostic Yield

• Colonoscopy with biopsies provides a specific diagnosis in 31-35% of patients with chronic diarrhea even when mucosa appears normal 4, 5
• Most common findings in bloody diarrhea: inflammatory bowel disease (ulcerative colitis, Crohn's disease), colorectal cancer, and microscopic colitis 6

Additional Investigations Based on Initial Findings

If colonoscopy is non-diagnostic or specific conditions are suspected:

For Suspected Small Bowel Disease

• MR enterography (preferred) or video capsule endoscopy 1
• Avoid barium studies due to poor sensitivity and specificity 1

For Suspected Bile Acid Malabsorption

• SeHCAT testing or serum 7α-hydroxy-4-cholesten-3-one measurement 1, 2
• Consider in patients with otherwise unexplained chronic diarrhea, as BAM is found in up to 42% of such cases 4

For Suspected Pancreatic Insufficiency

• Fecal elastase testing (preferred over older tests) 1, 2

For Suspected Small Bowel Bacterial Overgrowth

• Empirical trial of antibiotics (rifaximin, ciprofloxacin, metronidazole, or amoxicillin-clavulanic acid) 1, 2
• Glucose hydrogen breath testing if available 1

Common Pitfalls to Avoid

1. Inadequate colonic biopsies: Always take biopsies from right and left colon even if mucosa appears normal, as microscopic colitis can be present in macroscopically normal mucosa 1, 4

2. Missing terminal ileal disease: Ensure terminal ileal intubation when Crohn's disease is suspected 1

3. Overlooking bile acid malabsorption: Consider this diagnosis in patients with normal colonoscopy findings 4

4. Premature diagnosis of IBS: Ensure inflammatory and neoplastic conditions are excluded before making a functional diagnosis 1, 7

5. Inadequate infection screening: Always perform stool cultures and C. difficile testing, especially in immunocompromised or elderly patients 1, 3

Age-Specific Considerations

• All ages with bloody diarrhea: Full colonoscopy recommended regardless of age 1
• Under 40 years without rectal bleeding: Fecal calprotectin to exclude inflammation 1
• Over 45 years: Higher risk of colorectal neoplasia; colonoscopy is mandatory 1

By following this systematic approach, the etiology of chronic bloody diarrhea can be identified in the majority of cases, allowing for appropriate targeted therapy and improved patient outcomes.