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

Workup for Diarrhea

The recommended workup for a patient presenting with diarrhea should begin with a detailed clinical assessment to determine if the diarrhea is acute (<4 weeks) or chronic (≥4 weeks), followed by targeted laboratory testing based on clinical presentation and risk factors. 1

Initial Assessment

History - Key Elements to Obtain:

• Duration of symptoms (acute vs chronic)
• Stool characteristics (watery, bloody, mucous, purulent, greasy)
• Frequency of bowel movements and quantity
• Presence of dysenteric symptoms (fever, tenesmus, blood/pus in stool)
• Symptoms of volume depletion (thirst, tachycardia, orthostasis, decreased urination)
• Associated symptoms (nausea, vomiting, abdominal pain, cramps, headache, myalgias)
• Recent travel history
• Recent antibiotic use or hospitalization
• Immunocompromised status
• Dietary changes or food exposures
• Occupational exposures (food handler, daycare worker)
• Family history of GI disorders 2

Physical Examination - Focus On:

• Vital signs (fever, orthostatic changes)
• Signs of dehydration (dry mucous membranes, decreased skin turgor)
• Abdominal tenderness
• Altered mental status 2

Laboratory Testing

For Acute Diarrhea:

1. Limited testing for most cases of acute diarrhea - most are self-limiting viral infections 3

2. Testing indicated for:

   • Profuse, dehydrating diarrhea
   • Bloody or mucoid stools
   • Fever >38.5°C
   • Severe abdominal pain
   • Immunocompromised patients
   • Recent hospitalization or antibiotic use
   • Symptoms >7 days 2

3. Recommended tests when indicated:

   • Stool culture for bacterial pathogens (Salmonella, Shigella, Campylobacter, Yersinia)
   • C. difficile testing if recent antibiotic use or healthcare exposure
   • Giardia testing (antigen test or PCR) 2, 1

For Chronic Diarrhea (≥4 weeks):

1. Basic laboratory tests:

   • Complete blood count
   • Basic metabolic panel
   • C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR) - though less sensitive than fecal calprotectin/lactoferrin for intestinal inflammation 2, 1
   • Celiac disease serologies (IgA tissue transglutaminase and total IgA) 2, 1
   • Thyroid function tests

2. Stool studies:

   • Fecal calprotectin or lactoferrin (to screen for inflammatory bowel disease)
   • Giardia testing (strongly recommended regardless of travel history) 2, 1
   • Ova and parasites (only if travel to or immigration from high-risk areas) 2
   • Stool for occult blood 1

3. Specialized testing based on clinical suspicion:

   • Bile acid diarrhea testing (48-hour stool collection for total bile acids or serum fibroblast growth factor 19)
   • Consider empiric trial of bile acid binders if testing unavailable 1

Endoscopic Evaluation

Colonoscopy with biopsies is recommended for:

• Patients over 50 years
• Persistent diarrhea with weight loss
• Evaluation for microscopic colitis
• Bloody diarrhea
• Suspected inflammatory bowel disease 1

Red Flag Symptoms Requiring Urgent Referral

• Blood in stool
• Significant weight loss
• Clinical and laboratory signs of anemia
• Palpable abdominal mass
• Severe dehydration
• Persistent fever 3

Follow-Up Testing

• Follow-up testing is not recommended in most people after resolution of diarrhea
• Clinical and laboratory reevaluation may be indicated in people who do not respond to initial therapy
• Consider noninfectious conditions (IBD, IBS) in patients with symptoms lasting 14 or more days 2

Common Pitfalls to Avoid

1. Over-testing in acute, self-limiting diarrhea - Most cases resolve without specific intervention
2. Failure to test for Giardia - Recommended in all patients with chronic diarrhea regardless of travel history
3. Relying solely on ESR/CRP - Less sensitive than fecal calprotectin/lactoferrin for intestinal inflammation
4. Missing C. difficile infection - Always consider in patients with recent antibiotic use or healthcare exposure
5. Overlooking non-infectious causes - Consider medication side effects, IBD, celiac disease, and functional disorders

By following this structured approach to the workup of diarrhea, clinicians can efficiently diagnose the underlying cause and implement appropriate management strategies to improve patient outcomes.