Is diarrhea (loose stool) x11 without fever and normal white blood cell count more likely due to an infectious or non-infectious cause?

Diarrhea Without Fever or Leukocytosis: Infectious vs Non-Infectious

This presentation is more likely non-infectious, particularly viral gastroenteritis if acute, or non-infectious causes if prolonged, as the absence of fever and normal white blood cell count argue against invasive bacterial pathogens that typically cause inflammatory diarrhea. 1

Clinical Reasoning Based on Inflammatory Markers

The absence of fever and normal white blood cell count significantly reduces the likelihood of invasive bacterial pathogens:

• Bacterial infections (Shigella, Salmonella, Campylobacter) typically present with fever in 53-100% of cases and often cause leukocytosis or neutrophil predominance 1
• Fever is not highly discriminatory on its own, but its absence combined with normal WBC count makes bacterial dysentery-causing organisms less likely 1
• Patients infected with STEC (E. coli O157) usually are not febrile at presentation, representing an important exception to consider even without fever 1

Duration Matters for Differential Diagnosis

The clinical approach depends critically on symptom duration:

If Acute (<14 days):

• Viral gastroenteritis is most likely, particularly norovirus which causes vomiting and nonbloody diarrhea lasting 2-3 days, with low-grade fever in only 40% of cases 1, 2
• Norovirus accounts for 58% of gastroenteritis cases in the United States 2
• Toxigenic bacteria (enterotoxigenic E. coli, Staphylococcus aureus enterotoxin, Bacillus cereus) cause watery diarrhea without fever or inflammatory markers 1

If Persistent (≥14 days):

• Non-infectious causes become more likely, including post-infectious IBS, lactose intolerance, or inflammatory bowel disease 1
• Parasitic infections should be considered: Giardia, Cryptosporidium, Cyclospora, which can cause prolonged watery diarrhea without fever 1, 3
• Bacteria are unlikely to cause chronic diarrhea in immunocompetent individuals 3

When to Pursue Infectious Workup

Diagnostic testing is warranted despite absent fever/leukocytosis if:

• Diarrhea lasting ≥1 day (as in this case with 11 episodes), especially with dehydration, bloody stools, or recent antibiotic use 1
• Severe dehydration (dry mucous membranes, decreased urination, tachycardia, orthostasis) is present 1
• Recent travel, daycare attendance, or outbreak setting exists 1
• Immunocompromised status requires broader differential including opportunistic pathogens 1

Critical Pitfall to Avoid

Do not assume absence of fever and normal WBC excludes STEC infection, as E. coli O157 patients are typically afebrile at presentation but can develop life-threatening hemolytic uremic syndrome (HUS) 1. If bloody diarrhea develops, urgent stool testing for Shiga toxin is mandatory 1.

Practical Management Algorithm

For this specific presentation (11 loose stools, no fever, normal WBC):

1. Assess hydration status and provide oral rehydration as primary intervention 1
2. Obtain stool testing given the frequency (11 episodes suggests significant illness) for bacterial culture, viral studies if available, and parasites if symptoms persist >7 days 1
3. Avoid empiric antibiotics unless severe illness develops, as most cases are viral and antibiotics cause harm without benefit 2, 4
4. Reassess at 14 days if symptoms persist, considering non-infectious etiologies including lactose intolerance, IBS, or IBD 1

Peripheral white blood cell count and differential should not be used to establish etiology of diarrhea but may be clinically useful for assessing severity 1. The normal WBC in this case suggests viral or toxigenic bacterial cause rather than invasive bacterial infection, but does not definitively exclude infectious etiology 1.