What is the best course of treatment for a 20-year-old active duty female with a 1-day history of sharp diffuse stomach pain, non-bloody diarrhea, and vomiting, who is hemodynamically stable, afebrile, and has normal active bowel sounds, with recent close contact with a relative who had gastrointestinal symptoms?

Acute Gastroenteritis with Supportive Care and Close Monitoring

This 20-year-old presents with classic acute viral gastroenteritis following household exposure, and should be managed with oral rehydration, symptomatic treatment with antiemetics and loperamide, dietary modifications, and close outpatient monitoring for 24-48 hours—with clear return precautions for fever, severe dehydration, or worsening abdominal pain. 1, 2

Clinical Assessment and Risk Stratification

This patient's presentation is consistent with uncomplicated acute gastroenteritis based on several key features:

• Clear epidemiologic link to household contact with similar gastrointestinal symptoms strongly suggests viral etiology 2
• Hemodynamically stable and afebrile despite symptoms, indicating no current signs of severe dehydration or sepsis 1, 3
• Negative peritoneal signs (negative psoas and obturator signs) effectively rule out appendicitis despite right lower quadrant tenderness 3
• Normal active bowel sounds argue against obstruction or ileus 3

The bilateral cervical lymphadenopathy and mild pharyngeal erythema suggest a concurrent viral upper respiratory infection, which commonly accompanies viral gastroenteritis and supports the infectious etiology 1, 2

Immediate Management Approach

Hydration Strategy

• Aggressive oral rehydration with 8-10 large glasses of clear liquids daily (electrolyte solutions like Gatorade or broth preferred over plain water) 4, 1
• The patient's ability to keep some liquids down is reassuring and supports outpatient management 1
• Monitor for orthostatic symptoms (dizziness upon standing) which would indicate significant dehydration requiring IV fluids 4, 1

Symptomatic Treatment

• Ondansetron for nausea and vomiting to improve oral intake tolerance 1
• Loperamide 4mg initially, then 2mg after each unformed stool (maximum 16mg/day) to control diarrhea 4
• If no improvement after 24-48 hours on loperamide, reassess for complications 4

Dietary Modifications

• Stop all lactose-containing products immediately, as acute gastroenteritis can cause temporary lactose intolerance 4
• Frequent small meals with bland foods (bananas, rice, applesauce, toast, plain pasta) 4
• Avoid alcohol and high-osmolar supplements 4

When to Escalate Care

Return immediately or admit if any of the following develop:

• Fever ≥38°C (subjective fever at home warrants temperature monitoring) 4, 1
• Severe dehydration signs: inability to tolerate oral fluids, persistent vomiting, orthostatic hypotension, confusion 4, 1
• Worsening or severe abdominal pain, particularly if localized or associated with peritoneal signs 3
• Bloody diarrhea or more than 6 stools per day 4
• Symptoms persisting beyond 48-72 hours without improvement 4, 2

Diagnostic Testing Considerations

Currently NOT indicated given uncomplicated presentation:

• Stool studies (culture, ova and parasites, C. difficile) are unnecessary in acute watery diarrhea without fever, bloody stools, or severe illness 4, 1
• Complete blood count and electrolytes reserved for patients with severe symptoms or dehydration 1, 3
• Imaging (CT abdomen) not warranted with negative peritoneal signs and clear viral etiology 3

Pregnancy test should be obtained given the patient is a woman of reproductive age with abdominal pain and vomiting, despite recent LMP 3

Critical Pitfalls to Avoid

• Do not prescribe empiric antibiotics for acute watery diarrhea without evidence of severe illness, bloody diarrhea, or immunocompromise—this increases C. difficile risk and antibiotic resistance 4, 1
• Do not dismiss the subjective fever—instruct patient to document actual temperatures and return if ≥38°C develops, as fever with abdominal pain suggests bacterial superinfection 4, 1
• Do not overlook appendicitis despite negative special signs—if pain localizes to RLQ or worsens over 24 hours, urgent reassessment with imaging is required 3
• Monitor for post-infectious sequelae: military personnel and young adults can develop functional GI disorders (IBS, functional dyspepsia) following acute gastroenteritis 5

Follow-Up Plan

• Recheck in 24-48 hours by phone or in-person to assess symptom trajectory 4
• Document stool frequency and character to monitor response to treatment 4
• If symptoms persist beyond 7 days, consider stool studies and gastroenterology referral for evaluation of persistent infectious diarrhea 1, 2
• Infection control: patient should avoid food preparation and maintain strict hand hygiene until 48 hours after symptom resolution to prevent transmission 2