What is the appropriate workup and treatment for a patient presenting with diarrhea?

Workup and Treatment of Diarrhea

The appropriate workup for a patient with diarrhea should begin with determining whether it is acute or chronic, followed by assessment of severity and risk factors, with treatment tailored to the underlying cause and severity.

Initial Assessment

Classification by Duration

• Acute diarrhea: <4 weeks duration
• Persistent diarrhea: 2-4 weeks duration
• Chronic diarrhea: >4 weeks duration 1

Key History Elements

• Onset, duration, and frequency of diarrhea
• Stool characteristics (watery, bloody, fatty, mucus)
• Associated symptoms (fever, abdominal pain, vomiting, weight loss)
• Recent travel, antibiotic use, or hospitalization
• Dietary changes or food intolerances
• Medication review (antibiotics, laxatives, etc.)
• Past medical history (IBD, celiac disease, immunocompromised state)

Physical Examination Focus

• Vital signs (assess for fever, tachycardia, hypotension)
• Hydration status (skin turgor, mucous membranes, orthostatic changes)
• Abdominal examination (tenderness, distension, masses)
• Perianal examination (inflammation, fissures, fistulas)

Diagnostic Workup

Acute Diarrhea (<4 weeks)

1. Mild cases (no alarm features):

   • Generally no diagnostic testing needed 2
   • Empiric symptomatic treatment

2. When to test:

   • Bloody stools
   • Severe dehydration
   • Persistent fever >38.5°C
   • Severe abdominal pain
   • Immunocompromised patients
   • Recent hospitalization or antibiotic use
   • Symptoms >7 days 2

3. Initial tests:

   • Stool studies (culture, ova and parasites, C. difficile toxin if recent antibiotics)
   • CBC with differential
   • Basic metabolic panel
   • C-reactive protein

Chronic Diarrhea (>4 weeks)

1. Initial laboratory tests:

   • CBC, CRP, anti-tissue transglutaminase IgA, total IgA, basic metabolic panel 1
   • Thyroid function tests
   • Stool studies to categorize as watery, fatty, or inflammatory

2. Categorization of chronic diarrhea:

   • Watery: Fecal osmotic gap to differentiate osmotic vs. secretory
   • Fatty: Fecal fat, pancreatic elastase
   • Inflammatory: Fecal calprotectin, lactoferrin

3. Additional testing based on suspected etiology:

   • Endoscopy with biopsies (colonoscopy for inflammatory diarrhea, EGD for malabsorptive disorders)
   • Imaging studies (CT enterography, MR enterography)
   • Specialized tests (hydrogen breath test, SeHCAT scan for bile acid malabsorption)

Treatment Approach

Acute Diarrhea

1. Rehydration:

   • Oral rehydration solution (ORS) for mild to moderate dehydration
   • IV fluids for severe dehydration or inability to tolerate oral intake 2

2. Diet:

   • Continue regular diet with emphasis on easily digestible foods
   • BRAT diet (bread, rice, applesauce, toast) may be helpful
   • Avoid high-sugar foods, caffeine, and alcohol 2

3. Antimotility agents:

   • Loperamide: Initial dose 4 mg followed by 2 mg after each loose stool (maximum 16 mg/day) 3
   • Contraindicated in:
     • Bloody diarrhea
     • Suspected invasive bacterial infection
     • C. difficile infection
     • Children under 2 years 3

4. Antibiotics:

   • Generally not indicated for uncomplicated acute diarrhea 2
   • Consider for:
     • Bloody diarrhea with fever
     • Moderate to severe traveler's diarrhea
     • Suspected specific bacterial pathogens
   • Empiric options:
     • Azithromycin 500 mg once daily for 1-3 days
     • Fluoroquinolones where resistance is not a concern 2

Chronic Diarrhea

Treatment depends on the underlying cause:

1. Functional diarrhea/IBS-D:

   • Loperamide as needed
   • Dietary modifications (low FODMAP diet)
   • Bile acid sequestrants if bile acid malabsorption suspected 2

2. Inflammatory causes:

   • Treat underlying condition (IBD, microscopic colitis)
   • Corticosteroids, immunomodulators as appropriate

3. Malabsorptive disorders:

   • Gluten-free diet for celiac disease
   • Pancreatic enzyme replacement for exocrine insufficiency
   • Antibiotics for small intestinal bacterial overgrowth

4. Secretory diarrhea:

   • Bile acid sequestrants (cholestyramine, colestipol, colesevelam) for bile acid malabsorption 2
   • Octreotide for hormone-mediated secretory diarrhea 2

Special Considerations

Cancer Treatment-Related Diarrhea

1. Assessment:

   • Grade diarrhea according to National Cancer Institute Common Toxicity Criteria
   • Assess for dehydration and electrolyte imbalances 2

2. Management:

   • Grade 1-2: Hydration, electrolyte replacement, loperamide, and diet modification
   • Grade 3-4 or persistent Grade 2: Consider hospitalization, IV fluids, octreotide (100-150 μg SC/IV TID, can be titrated up to 500 μg TID) 2
   • Consider antibiotics for neutropenic patients 2

Complications and Warning Signs

• Severe dehydration
• Electrolyte abnormalities
• Acute kidney injury
• Sepsis in infectious causes
• Toxic megacolon in inflammatory conditions

Follow-up

• Reassess if symptoms persist beyond expected duration
• Consider referral to gastroenterology for chronic diarrhea not responding to initial management
• Evaluate for non-infectious conditions if diarrhea persists >14 days 2

Remember that empiric treatment should be avoided in patients with persistent watery diarrhea lasting 14 days or more, as this may mask underlying pathology 2.