What is the initial approach to managing a patient with chronic diarrhea?

Initial Management of Chronic Diarrhea

The initial approach to managing chronic diarrhea should include a detailed history and physical examination, first-line laboratory tests, and stool studies to categorize the diarrhea as watery, fatty, or inflammatory, which will guide subsequent targeted investigations and treatment. 1

Definition and Initial Assessment

Chronic diarrhea is defined as:

• Abnormal passage of ≥3 loose stools per day for more than 4 weeks 1
• May present as a change in stool consistency, frequency, urgency, or volume
• Bristol stool chart type 5 and above is recommended for objective assessment 1

Step 1: History and Physical Examination

Key Historical Elements:

• Duration of symptoms (>4 weeks defines chronic diarrhea)
• Stool characteristics (watery, bloody, greasy, mucous)
• Pattern (continuous vs. intermittent, nocturnal, relationship to meals)
• Presence of alarm features:
  • Weight loss
  • Nocturnal diarrhea
  • Blood in stool
  • Recent onset (<3 months)
  • Fever

Important Risk Factors to Assess:

1. Previous surgery: Terminal ileal resection, cholecystectomy, gastric surgery 1
2. Family history: IBD, colorectal cancer, celiac disease 1
3. Medications: Antibiotics, antacids, laxatives, metformin
4. Diet: Excessive caffeine, alcohol, artificial sweeteners, FODMAPs
5. Systemic diseases: Thyroid disorders, diabetes, adrenal disease 1
6. Travel history: Exposure to infectious agents

Step 2: First-Line Investigations in Primary Care

The British Society of Gastroenterology recommends the following initial tests 1:

• Complete blood count
• C-reactive protein
• Electrolytes and liver function tests
• Thyroid function tests
• Serological tests for celiac disease (anti-tissue transglutaminase IgA and total IgA)
• Stool studies if infectious etiology or inflammation is suspected

Step 3: Categorize the Diarrhea Type

Based on initial findings, categorize the diarrhea as:

1. Watery diarrhea:

   • Secretory (persists with fasting)
   • Osmotic (improves with fasting)
   • Functional (IBS-D, functional diarrhea)

2. Fatty diarrhea (malabsorption):

   • Characterized by steatorrhea, weight loss, excess gas
   • Consider celiac disease, pancreatic insufficiency, small bowel bacterial overgrowth

3. Inflammatory diarrhea:

   • Blood or pus in stool
   • Elevated inflammatory markers
   • Consider IBD, microscopic colitis, infectious colitis

Step 4: Targeted Investigations Based on Category

For Watery Diarrhea:

• Consider SeHCAT test or C4 assay for bile acid malabsorption, particularly in patients with risk factors like terminal ileal resection or cholecystectomy 1
• Colonoscopy with biopsies for microscopic colitis, especially in older patients

For Fatty Diarrhea:

• Upper endoscopy with duodenal biopsies if celiac disease is suspected
• Pancreatic function tests (fecal elastase) for pancreatic insufficiency
• Hydrogen/methane breath tests for small bowel bacterial overgrowth

For Inflammatory Diarrhea:

• Colonoscopy with biopsies
• Stool calprotectin
• Stool culture and C. difficile testing

Step 5: Initial Management

General Measures:

• Fluid and electrolyte replacement if dehydration is present
• Dietary modifications based on suspected etiology
• Symptomatic relief with antidiarrheal agents like loperamide for non-infectious causes 2
  • Initial dose: 4 mg followed by 2 mg after each unformed stool
  • Maximum daily dose: 16 mg

Specific Treatments Based on Diagnosis:

• For bile acid diarrhea: Cholestyramine 1
• For IBS-D: Consider rifaximin 550 mg three times daily for 14 days 3
• For microscopic colitis: Budesonide
• For small bowel bacterial overgrowth: Appropriate antibiotics

When to Refer to Secondary Care

Referral to gastroenterology is indicated when:

• Alarm features are present (weight loss, blood in stool, nocturnal symptoms)
• First-line investigations are normal but symptoms persist and affect quality of life
• Symptoms are severe or not responding to initial management
• Age >45 years with recent change in bowel habit (to exclude colorectal cancer) 1

Common Pitfalls to Avoid

1. Misdiagnosing functional disorders: IBS-D, microscopic colitis, and bile acid diarrhea can present similarly but require different treatments 1

2. Overlooking medication-induced diarrhea: Always review current medications

3. Confusing fecal incontinence with diarrhea: Clarify the patient's definition of "diarrhea"

4. Inadequate testing: Failure to categorize diarrhea type can lead to unnecessary or insufficient investigations

5. Empiric treatment without diagnosis: While symptomatic treatment is appropriate initially, persistent symptoms require a specific diagnosis for targeted therapy

By following this systematic approach, the underlying cause of chronic diarrhea can be identified in the majority of cases, leading to appropriate treatment and improved outcomes for patients.