What are the initial diagnostic tests and treatment options for a patient presenting with increased stool frequency?

Initial Diagnostic Tests and Treatment Options for Increased Stool Frequency

For patients presenting with increased stool frequency, initial diagnostic testing should include screening blood tests (full blood count, ferritin, tissue transglutaminase/EMA, and thyroid function test) and stool tests for inflammation (faecal calprotectin), which should be undertaken in primary care. 1

Initial Diagnostic Approach

Step 1: Categorize the Diarrhea

• Determine duration:
  • Acute: <4 weeks
  • Chronic: >4 weeks
• Assess stool characteristics using Bristol stool chart:
  • Consistency
  • Frequency
  • Presence of blood, mucus, or fat

Step 2: Initial Laboratory Testing

• Blood tests:

  • Complete blood count (to assess for anemia, infection)
  • Ferritin (to evaluate iron stores)
  • Tissue transglutaminase antibodies and total IgA (to screen for celiac disease)
  • Thyroid function tests (to rule out hyperthyroidism)
  • C-reactive protein (to assess inflammation)

• Stool tests:

  • Faecal calprotectin (key test to distinguish inflammatory from non-inflammatory causes)
  • Stool for ova, cysts, and parasites (especially if travel history or persistent symptoms)
  • Clostridium difficile testing (particularly if recent antibiotic use or healthcare exposure)

Step 3: Additional Testing Based on Clinical Suspicion

• For suspected inflammatory bowel disease:

  • Elevated faecal calprotectin (>150 μg/g) warrants endoscopic assessment 1
  • Normal calprotectin (<50 μg/g) makes inflammatory bowel disease less likely

• For suspected infection:

  • Examination of three fresh stools for ova, cysts, and parasites (60-90% sensitivity)
  • Stool ELISA for Giardia (92% sensitivity, 98% specificity) if persistent symptoms 1
  • Two-stage testing for C. difficile (glutamate dehydrogenase EIA or PCR followed by toxin EIA) 1

• For suspected malabsorption:

  • If IgA deficient, use IgG EMA or IgG TTG to screen for celiac disease 1
  • Consider lactose/dextrose H2 breath test for suspected lactose intolerance 1

Step 4: Structural Evaluation When Indicated

• Colonoscopy is recommended for:
  • Patients >50 years with new onset symptoms
  • Presence of alarm symptoms (weight loss, rectal bleeding, anemia)
  • Persistently elevated inflammatory markers despite normal stool tests
  • Family history of colorectal cancer or inflammatory bowel disease

Initial Treatment Options

For Non-Inflammatory Diarrhea (Normal Calprotectin)

1. Dietary modifications:

   • Trial of fiber supplementation for constipation-predominant symptoms
   • Elimination of potential dietary triggers (lactose, gluten, FODMAPs as appropriate)

2. For suspected IBS-D:

   • Antispasmodic medications (e.g., dicyclomine) - 82% of patients with IBS respond favorably to dicyclomine at initial doses of 160 mg daily compared to 55% with placebo 2
   • Trial of loperamide for diarrhea-predominant symptoms 1

3. For suspected functional diarrhea:

   • Loperamide as needed
   • Consider bile acid sequestrants if bile acid malabsorption is suspected

For Inflammatory Diarrhea (Elevated Calprotectin)

• Refer for gastroenterology evaluation and endoscopic assessment rather than empiric treatment 1
• Treatment will depend on specific diagnosis (IBD, microscopic colitis, etc.)

For Infectious Diarrhea

• For confirmed Giardia infection:
  • Short course of metronidazole or tinidazole 1
• For C. difficile infection:
  • Appropriate antibiotic therapy based on severity
  • Avoid unnecessary antimicrobial therapy based on PCR alone without evidence of toxin production 1

Important Caveats and Pitfalls

1. Don't miss immunodeficiency states:

   • Consider HIV testing in regions with significant prevalence, as chronic diarrhea is common in newly diagnosed HIV 1

2. Avoid excessive testing in typical IBS presentations:

   • Patients meeting symptom criteria for IBS without alarm features do not require extensive testing 3
   • The yield of serologic testing for celiac disease in IBS patients is relatively low 3

3. Be cautious with antimicrobial therapy:

   • Post-infectious IBS can occur after C. difficile infection
   • Avoid excessive antimicrobial therapy based solely on PCR without evidence of toxin production 1

4. Remember that chronic diarrhea can have multiple causes:

   • Consider overlapping conditions, especially in patients with partial response to initial therapy

By following this structured approach to diagnosis and treatment, most cases of increased stool frequency can be appropriately managed, with timely referral for specialized care when indicated.