What is the best course of treatment for a patient presenting with abdominal pain, nausea, vomiting, and diarrhea?

Management of Acute Gastroenteritis with Abdominal Pain, Nausea, Vomiting, and Diarrhea

Oral rehydration solution (ORS) is the cornerstone of treatment and should be initiated immediately as first-line therapy for mild to moderate dehydration, with ondansetron considered to facilitate oral intake if vomiting is significant. 1, 2

Immediate Assessment and Risk Stratification

Assess dehydration severity through specific clinical signs:

• Mild dehydration (3-5% fluid deficit): Slightly dry mucous membranes, normal vital signs, decreased urine output 2
• Moderate dehydration (6-9% fluid deficit): Loss of skin turgor with tenting, dry mucous membranes, sunken eyes, decreased capillary refill 1, 2
• Severe dehydration (≥10% fluid deficit): Severe lethargy or altered consciousness, prolonged skin tenting (>2 seconds), cool and poorly perfused extremities, rapid deep breathing indicating acidosis 2

Identify red flags requiring immediate hospitalization:

• Severe dehydration with signs of shock or altered mental status 1
• Bloody diarrhea with fever and systemic toxicity (suggests bacterial infection such as Salmonella, Shigella, or enterohemorrhagic E. coli) 1, 2
• Persistent vomiting despite small-volume ORS administration 2
• Absent bowel sounds on auscultation (absolute contraindication to oral rehydration) 2
• Severe abdominal pain disproportionate to examination findings 1

Rehydration Protocol

For mild to moderate dehydration (outpatient management):

• Administer reduced osmolarity ORS at 50-100 mL/kg over 2-4 hours 1, 2, 3
• If vomiting is present, use small frequent volumes (5-10 mL) every 1-2 minutes via spoon or syringe, gradually increasing as tolerated 1, 2, 3
• Replace ongoing losses continuously: 10 mL/kg ORS for each watery stool and 2 mL/kg for each vomiting episode 1, 2
• Reassess hydration status after 2-4 hours; if still dehydrated, reestimate deficit and restart rehydration 2

For severe dehydration (inpatient management):

• Administer isotonic intravenous fluids (lactated Ringer's or normal saline) immediately 1
• Continue IV rehydration until pulse, perfusion, and mental status normalize 1
• Transition to ORS to replace remaining deficit once patient improves and can tolerate oral intake 1, 2

Antiemetic Therapy

Ondansetron is recommended to facilitate oral rehydration when vomiting is significant:

• Adults: 8 mg orally once, may repeat every 8 hours as needed 4
• Children >4 years and adolescents: 4 mg orally for ages 4-11 years; 8 mg for ages 12-17 years 1, 4
• Do NOT use in children <4 years of age 1
• Ondansetron reduces vomiting rate, improves tolerance of oral rehydration, and reduces need for IV rehydration 5

Important ondansetron precautions:

• Avoid in patients with congenital long QT syndrome 4
• Monitor for serotonin syndrome if patient is taking SSRIs, SNRIs, or other serotonergic drugs 4
• Monitor for signs of myocardial ischemia (chest pain, shortness of breath) 4
• Be aware that ondansetron may mask progressive ileus or gastric distension—monitor for decreased bowel activity 4

Nutritional Management

Resume normal diet early:

• Continue breastfeeding throughout the diarrheal episode in infants 1, 2, 3
• Resume age-appropriate normal diet during or immediately after rehydration is complete 1, 2, 3
• Early refeeding reduces severity and duration of illness 2

Avoid these dietary items during acute illness:

• Foods high in simple sugars (soft drinks, undiluted apple juice) as they can exacerbate diarrhea through osmotic effects 2
• Caffeinated beverages (coffee, tea, energy drinks) as they stimulate intestinal motility and worsen diarrhea 1, 2
• High-fat foods 2

Antidiarrheal Medications

Loperamide use is restricted and conditional:

• May be given to immunocompetent adults with acute watery diarrhea once adequately hydrated 1, 3
• NEVER give to children <18 years of age with acute diarrhea due to risk of serious adverse events including ileus and deaths 1, 3
• Avoid at any age in suspected or proven inflammatory diarrhea, diarrhea with fever, or bloody diarrhea due to risk of toxic megacolon 1, 3

Adjunctive Therapies

Probiotics may be considered:

• May reduce symptom severity and duration in immunocompetent adults and children 1, 3
• Take for up to 12 weeks; discontinue if no improvement 1
• Specific organism, route, and dosage recommendations vary—consult literature or manufacturer guidance 1

Zinc supplementation:

• Reduces duration of diarrhea in children 6 months to 5 years of age who reside in countries with high prevalence of zinc deficiency or who have signs of malnutrition 1

Antimicrobial Therapy

Antimicrobial treatment is NOT routinely indicated:

• Most acute gastroenteritis is viral and self-limited 2
• Consider antimicrobials only in specific cases: bloody diarrhea with fever, recent antibiotic use (C. difficile concern), exposure to certain pathogens, recent foreign travel, or immunodeficiency 2
• Modify or discontinue antimicrobials when a clinically plausible organism is identified 1

Infection Control Measures

Implement strict infection control:

• Practice proper hand hygiene after using toilet, before eating, and after handling soiled items 2
• Use gloves and gowns when caring for patients with diarrhea 2
• Clean and disinfect contaminated surfaces promptly 2
• Separate ill persons from well persons until at least 2 days after symptom resolution 2

Common Pitfalls to Avoid

• Do not delay rehydration while awaiting diagnostic testing—initiate ORS immediately 2
• Do not use inappropriate fluids like sports drinks or apple juice as primary rehydration solutions for moderate to severe dehydration 2
• Do not administer antimotility drugs to children or in cases of bloody diarrhea 1, 3
• Do not unnecessarily restrict diet during or after rehydration—early refeeding is beneficial 1, 2, 3
• Do not use metoclopramide in acute gastroenteritis—it has no role and may worsen symptoms by accelerating transit 2
• Do not rely on antidiarrheal agents as they shift focus away from appropriate fluid, electrolyte, and nutritional therapy 2