How do you diagnose and manage Acute Gastroenteritis (AGE) and what are the criteria for hospital admission?

Diagnosis and Management of Acute Gastroenteritis

Diagnose AGE clinically based on ≥3 loose/liquid stools per 24 hours with or without vomiting, nausea, fever, or abdominal pain, and immediately assess hydration status to guide treatment—oral rehydration solution is first-line therapy for mild-to-moderate dehydration, while severe dehydration, shock, altered mental status, or failure of oral rehydration mandates hospital admission for intravenous fluids. 1, 2

Clinical Diagnosis

AGE is defined by passage of 3 or more loose or liquid stools per 24 hours, or more frequently than normal for the individual, often accompanied by vomiting, nausea, fever, or abdominal pain 1. The diagnosis is primarily clinical and does not require routine stool testing when viral gastroenteritis is the likely etiology 3.

Key diagnostic features to assess:

• Duration of symptoms: acute (<7 days), prolonged (7-13 days), persistent (14-29 days), or chronic (≥30 days) 1
• Presence of blood or mucus in stool (suggests bacterial etiology or inflammatory diarrhea) 1
• Recent antibiotic use, travel history, outbreak exposure, or immunocompromised status 2
• Bilious emesis or forceful vomiting (raises concern for obstruction, particularly in infants) 1

Hydration Assessment

Immediately evaluate hydration status through specific physical examination findings: 2, 3

• Skin turgor (decreased indicates dehydration)
• Mucous membrane moisture (dry membranes suggest dehydration)
• Mental status (altered consciousness indicates severe dehydration)
• Capillary refill time (prolonged >2 seconds suggests dehydration)
• Vital signs: tachycardia, hypotension
• Urine output (decreased frequency/volume)
• In children: sunken eyes, sunken fontanelle

Categorize dehydration severity: 2, 4

• Mild: 3-5% body weight loss (<4% in some classifications)
• Moderate: 6-9% body weight loss (4-6% in some classifications)
• Severe: ≥10% body weight loss (>6% in some classifications)

Laboratory testing is not routinely recommended for assessing dehydration, as no single value accurately predicts severity 5. However, low serum bicarbonate combined with clinical parameters may support the diagnosis 5.

Treatment Algorithm

Mild-to-Moderate Dehydration (Outpatient Management)

Oral rehydration solution (ORS) is the first-line treatment: 2, 4

• Use low-osmolarity ORS formulations (preferred over sports drinks or juices) 2
• Dosing: 50-100 mL/kg over 3-4 hours for children; 2-4 L for adults 4
• Continue ORS to replace ongoing losses until diarrhea and vomiting resolve 2
• Nasogastric administration may be considered if patient refuses oral intake 2

Nutritional management: 2, 4

• Continue breastfeeding throughout the illness in infants 2, 4
• Resume age-appropriate diet during or immediately after rehydration 2, 4
• Early refeeding is recommended rather than fasting or restrictive diets 1, 2
• Avoid foods high in simple sugars (soft drinks, undiluted apple juice) as they worsen diarrhea through osmotic effects 2

Pharmacological adjuncts (once adequately hydrated): 1, 2

• Ondansetron: May be given to children >4 years and adolescents to facilitate oral rehydration when vomiting is significant 1, 2. This reduces immediate need for hospitalization and improves tolerance of ORS 1, 5
• Loperamide: May be given to immunocompetent adults with acute watery diarrhea 1, 2, 4. Never give to children <18 years 1, 2. Avoid in bloody diarrhea, fever, or suspected inflammatory diarrhea due to risk of toxic megacolon 1
• Probiotics: May reduce symptom severity and duration 2
• Zinc supplementation: Reduces diarrhea duration in children 6 months to 5 years in areas with high zinc deficiency or malnutrition 2

Antimicrobials are generally NOT indicated: 2, 4

• Viral agents are the predominant cause of AGE 2
• Consider only in specific cases: bloody diarrhea with fever, recent antibiotic use, exposure to certain pathogens, recent foreign travel, or immunodeficiency 2

Severe Dehydration or Failed Oral Rehydration (Hospital Admission Required)

Admit to hospital for intravenous rehydration when: 2, 4

• Severe dehydration (≥10% body weight loss)
• Signs of shock (hypotension, altered perfusion)
• Altered mental status
• Failure of oral rehydration therapy
• Ileus
• Inability to tolerate oral intake despite antiemetics

Intravenous fluid management: 2, 4

• Use isotonic fluids: lactated Ringer's or normal saline 2, 4
• Administer 20 mL/kg boluses in children 4
• Continue IV rehydration until pulse, perfusion, and mental status normalize 2
• Transition to ORS to replace remaining deficit once patient improves 2

Infection Control Measures

Implement strict precautions to prevent transmission: 2

• Hand hygiene with soap and water after toilet use, diaper changes, before/after food preparation, and before eating 2
• Use gloves and gowns when caring for patients with diarrhea 2
• Clean and disinfect contaminated surfaces promptly 2
• Isolate ill persons from well persons until at least 2 days after symptom resolution 2

Critical Pitfalls to Avoid

• Do not delay rehydration while awaiting diagnostic testing—initiate treatment immediately 2
• Do not use inappropriate fluids (apple juice, sports drinks) as primary rehydration for moderate-to-severe dehydration 2
• Never give antimotility drugs to children or in cases of bloody diarrhea 1, 2
• Do not unnecessarily restrict diet during or after rehydration 1, 2
• Do not routinely use antimicrobials—they have limited usefulness since viral agents predominate 2
• Avoid antimicrobials in STEC O157 infections as they increase risk of hemolytic uremic syndrome 4