No Additional Testing is Necessary (Answer D)
For this patient with uncomplicated acute watery diarrhea, normal vital signs, normal laboratory values, and no risk factors, no additional diagnostic testing is indicated at this time. 1
Clinical Reasoning
This patient presents with classic self-limited acute gastroenteritis that does not meet criteria for diagnostic workup:
- Non-bloody, watery diarrhea for only 24 hours with mild symptoms 1
- Normal vital signs with temperature only 37.8°C (100.0 F), which is minimally elevated 1
- Moist mucous membranes indicating adequate hydration 2
- Normal CBC and metabolic panel excluding severe dehydration, electrolyte abnormalities, or leukocytosis 1
- No risk factors: no recent travel, antibiotic use, hospitalization, or immunocompromise 1
When Testing IS Indicated
The 2017 IDSA guidelines specify that diagnostic testing should be reserved for specific high-risk scenarios, none of which apply here 1:
- Signs of severe dehydration (this patient has moist mucous membranes) 1
- Bloody or mucoid stools (this patient has watery diarrhea) 1, 2
- Persistent fever documented in medical setting (temperature is only 37.8°C) 1
- Immunocompromised patients (no history provided) 1
- Suspected nosocomial infection (no recent hospitalization) 1
- Persistent symptoms beyond 7 days (only 24 hours duration) 2, 3
Why Each Test is NOT Needed
Stool culture (Option A): Not indicated for uncomplicated acute watery diarrhea in immunocompetent patients without bloody stools, high fever, or severe illness 1, 2. Most acute diarrhea is viral and self-limited 2, 3.
Fecal lactoferrin (Option B): This inflammatory marker is used to distinguish inflammatory from non-inflammatory diarrhea, but testing is unnecessary when the patient lacks features of inflammatory diarrhea (no blood, minimal fever, mild symptoms) 1.
C. difficile testing (Option C): Only indicated with recent antibiotic use, recent hospitalization, or healthcare exposure—none of which this patient has 1. Testing without risk factors leads to false positives and inappropriate treatment 1.
Appropriate Management
The correct approach for this patient is supportive care 1, 2:
- Oral rehydration with 8-10 glasses of clear liquids daily 1, 2
- Dietary modifications: avoid lactose, alcohol, high-osmolar supplements; eat small frequent meals (BRAT diet) 1, 2
- Symptomatic treatment with loperamide if needed: 4 mg initial dose, then 2 mg after each unformed stool (maximum 16 mg/day) 4, 2
- Reassurance that most acute diarrhea resolves within 48-72 hours 2, 3
Critical Pitfall to Avoid
Overtesting in uncomplicated acute diarrhea is a common error that increases costs, delays, and may lead to unnecessary antibiotic use 1, 2. The majority of acute diarrheal illness in immunocompetent patients is self-limited viral gastroenteritis requiring only supportive care 2, 3. Testing should be targeted to patients with specific risk factors or severe presentations 1, 3.