What is the best course of action for managing symptoms of diarrhea, abdominal cramps, and vomiting in a 15-year-old male?

Management of Acute Gastroenteritis in a 15-Year-Old Male

This 15-year-old male requires immediate oral rehydration solution (ORS) as first-line therapy, ondansetron to facilitate oral intake given daily vomiting, and early resumption of normal diet—antimotility agents and empiric antibiotics are contraindicated. 1

Immediate Rehydration Strategy

Assess hydration status first by evaluating skin turgor, mental status, mucous membrane moisture, capillary refill, and vital signs to categorize dehydration severity. 1, 2 Given 4 days of constant diarrhea with daily vomiting and prolonged toilet sitting, this patient likely has moderate dehydration (6-9% fluid deficit). 1, 2

Oral Rehydration Protocol

• Administer reduced osmolarity ORS at 100 mL/kg over 2-4 hours for moderate dehydration—this is approximately 5-6 liters for an average 15-year-old male. 1, 2

• Start with small volumes (5-10 mL every 1-2 minutes) using a spoon or syringe, gradually increasing as tolerated to prevent triggering more vomiting. 2, 3

• Replace ongoing losses: administer 10 mL/kg ORS for each watery stool and 2 mL/kg for each vomiting episode throughout the rehydration process. 1, 2

• Reassess hydration status after 2-4 hours—if still dehydrated, reestimate the deficit and restart rehydration therapy. 1, 2

When to Escalate to IV Therapy

• Reserve intravenous rehydration only if the patient develops severe dehydration (≥10% deficit), shock, altered mental status, or fails oral rehydration attempts. 1, 2

• If IV therapy becomes necessary, use isotonic fluids (lactated Ringer's or normal saline) and continue until pulse, perfusion, and mental status normalize, then transition back to ORS. 1, 2

Antiemetic Management

Ondansetron is specifically indicated for this patient given his age (>4 years) and significant daily vomiting that interferes with oral rehydration. 1, 3

• Administer ondansetron 0.15 mg/kg (maximum 16 mg) to facilitate tolerance of oral rehydration—this is an adjunctive treatment, not a substitute for fluid therapy. 3

• Exercise caution if the patient has underlying heart disease due to potential QT interval prolongation. 3

• Ondansetron may paradoxically increase stool volume while reducing vomiting, but this does not contraindicate its use when vomiting prevents adequate oral intake. 4

Nutritional Management

• Resume age-appropriate normal diet immediately during or after rehydration is completed—early refeeding reduces illness severity and duration. 1, 2

• Avoid foods high in simple sugars (soft drinks, undiluted apple juice) as they can exacerbate diarrhea through osmotic effects. 2

• Recommended foods include starches, cereals, yogurt, fruits, and vegetables. 1

Critical Contraindications

Antimotility Agents Are Prohibited

• Loperamide must not be given to this patient as he is under 18 years of age—this is a strong contraindication regardless of symptom severity. 1, 2

• Loperamide works through opioid receptor agonism to reduce intestinal motility and could increase risk of serious complications in infectious diarrhea. 4

Empiric Antibiotics Are Not Indicated

• Do not prescribe empiric antimicrobial therapy for this acute watery diarrhea without recent international travel—viral agents are the predominant cause and antibiotics have limited usefulness. 1, 2

• The history of moldy cafeteria food suggests foodborne illness, but empiric treatment is still not recommended in immunocompetent adolescents with watery diarrhea. 1

Monitoring and Red Flags

• Monitor for warning signs requiring immediate escalation: decreased urine output, lethargy or altered mental status, worsening abdominal pain, bloody stools, or high fever. 2

• Track vital signs every 2-4 hours including capillary refill, skin turgor, and mental status to assess for progression to severe dehydration. 2

• If bloody diarrhea develops, immediately discontinue ondansetron and reassess for inflammatory diarrhea requiring different management. 3

Infection Control Measures

• Advise strict hand hygiene after using the toilet, before eating, and before food preparation to prevent transmission to household contacts. 2

• Separate the patient from well household members until at least 2 days after symptom resolution. 2

• Asymptomatic household contacts do not require preventive therapy but should follow infection control measures. 1

Common Pitfalls to Avoid

• Do not delay rehydration while awaiting diagnostic testing—begin ORS immediately based on clinical assessment. 2

• Do not use sports drinks or apple juice as primary rehydration solutions—these lack appropriate sodium content and have excessive sugar. 2, 3

• Do not prescribe ondansetron without ensuring proper ORS administration technique—these are complementary interventions, not sequential. 3

• Do not unnecessarily restrict diet—fasting or restrictive diets prolong illness duration. 2