What does the presence of white blood cells (leukocytes) in stool indicate and how is it treated?

White Blood Cells in Stool: Diagnostic Significance and Management

The presence of white blood cells (leukocytes) in stool primarily indicates inflammatory diarrhea, which is most commonly caused by invasive bacterial pathogens, but should not be used alone to establish the specific cause of infectious diarrhea.

Diagnostic Significance

What Leukocytes in Stool Indicate:

• Inflammatory Process: Fecal leukocytes suggest an inflammatory process in the intestinal mucosa 1
• Potential Causes:
  • Invasive bacterial infections (Shigella, Salmonella, Campylobacter, enteroinvasive E. coli)
  • Inflammatory bowel disease (IBD)
  • Certain parasitic infections
  • Some viral infections

Diagnostic Value and Limitations:

• Limited Specificity: Fecal leukocyte examination has poor specificity for establishing the infectious cause of diarrhea 1
• IDSA Guidelines Recommendation: The 2017 IDSA guidelines strongly recommend against using fecal leukocyte examination to establish the cause of acute infectious diarrhea 1
• Poor Performance: Fecal leukocyte morphology degrades during transport and processing, making accurate recognition difficult 1
• Intermittent Presence: In inflammatory diarrhea, fecal leukocytes are intermittently present and unevenly distributed in stool, limiting sensitivity 1

Better Alternatives:

• Fecal Lactoferrin/Calprotectin: These are more reliable surrogate markers for intestinal inflammation as they are not degraded during transport and processing 1
• Stool Culture: More definitive for identifying specific bacterial pathogens 1

Diagnostic Approach

Initial Assessment:

1. Stool Testing Indications:

   • Acute community-acquired diarrhea with fever
   • Bloody stools
   • Severe abdominal pain
   • Diarrhea lasting >1 day
   • Immunocompromised patients
   • Recent antibiotic use
   • Healthcare-associated diarrhea

2. Recommended Tests:

   • Stool culture for bacterial pathogens
   • C. difficile testing (especially with recent antibiotic use or healthcare exposure)
   • Consider molecular diagnostic panels where available 1

Specific Testing Based on Clinical Presentation:

• For Bloody Diarrhea: Test for STEC (Shiga toxin-producing E. coli), Shigella, Salmonella, and Campylobacter 1
• For Persistent Diarrhea (>7 days): Consider additional testing for parasites 1
• For Healthcare-Associated Diarrhea: Prioritize C. difficile testing 1

Treatment Approach

Treatment is Based on Identified Pathogen:

1. Supportive Care:

   • Oral or IV rehydration based on dehydration severity
   • Electrolyte replacement
   • Symptomatic treatment

2. Antimicrobial Therapy:

   • Only indicated for specific pathogens or severe disease
   • Avoid antibiotics for STEC infections as they may increase risk of hemolytic uremic syndrome (HUS) 1
   • Avoid antidiarrheal medications in suspected inflammatory bacterial diarrhea as they may worsen illness 1

3. Pathogen-Specific Treatment:

   • Shigellosis: Appropriate antibiotics based on susceptibility
   • Salmonellosis: Usually self-limiting; antibiotics only for invasive disease
   • Campylobacter: Consider macrolides for severe disease
   • C. difficile: Oral vancomycin or fidaxomicin

For Inflammatory Bowel Disease:

• If infectious causes are ruled out and IBD is suspected, referral to gastroenterology for colonoscopy with biopsies is recommended 1
• Treatment will depend on the type and severity of IBD

Monitoring and Follow-up

• Serial Monitoring: For patients with severe disease, monitor hemoglobin, platelet counts, electrolytes, BUN and creatinine to detect complications like HUS 1
• Follow-up Testing: Routine follow-up stool testing is not recommended after resolution of symptoms in most cases 1

Important Considerations

• The combination of fecal leukocytes AND fecal blood has better predictive value for bacterial pathogens than either finding alone 2
• White blood cells in stool should not be used as the sole criterion for STEC testing or other pathogen-specific testing 1
• Early diagnosis and appropriate management of specific pathogens can prevent complications and limit spread 1

Remember that while fecal leukocytes suggest inflammation, they cannot reliably distinguish between specific causes of inflammatory diarrhea, and comprehensive stool testing is necessary for definitive diagnosis.