What is the definition, causes, clinical features, investigation, and management of acute gastroenteritis in children, particularly those under 6 months old, according to the Indian Academy of Pediatrics (IAP) guidelines?

Acute Gastroenteritis in Children: IAP-Aligned Management

Definition

Acute gastroenteritis is defined as acute onset of vomiting and/or diarrhea (increased frequency and decreased consistency of stools), typically lasting less than 7 days 1. Duration categories include: acute (<7 days), prolonged (7-13 days), persistent (14-29 days), and chronic (≥30 days) 1.

Causes

Viral Pathogens (Predominant)

• Norovirus is the most common pathogen in hospitalized children (27%), responsible for 58% of all gastroenteritis cases 1
• Rotavirus is the second most common (21% in hospitalized children), though previously the leading cause before vaccine introduction 1
• Adenovirus accounts for 14% of viral cases 2

Bacterial and Parasitic Causes

• Bacterial pathogens include Shigella, Salmonella, enterohemorrhagic E. coli, and Vibrio cholerae (more common in resource-constrained settings) 3
• Parasitic infections include Giardia (particularly in day care settings) 4
• Bloody diarrhea or white blood cells on methylene blue stain suggests bacterial invasion requiring stool cultures 4

Clinical Features

Typical Presentation

• Gastroenteritis begins with acute onset of fever and vomiting, followed 24-48 hours later by watery diarrhea 1
• Symptoms generally persist 3-8 days 1
• Vomiting occurs in 80-90% of infected children, usually lasts <24 hours 1
• Diarrhea typically consists of 10-20 bowel movements per day 1

Dehydration Assessment (Critical for Management)

Categorize dehydration severity based on clinical signs 5:

Mild Dehydration (3-5% fluid deficit)

• Slightly decreased skin turgor 5
• Moist mucous membranes 5
• Normal mental status 5

Moderate Dehydration (6-9% fluid deficit)

• Loss of skin turgor with tenting when pinched 5
• Dry mucous membranes 5
• Decreased urine output 5

Severe Dehydration (≥10% fluid deficit) - MEDICAL EMERGENCY

• Severe lethargy or altered consciousness 1
• Prolonged skin tenting (>2 seconds) 1
• Cool and poorly perfused extremities, decreased capillary refill 1
• Rapid, deep breathing indicating metabolic acidosis 1

Red Flags Requiring Immediate Attention

• Altered mental status 1
• Absent bowel sounds (contraindication to oral therapy) 5
• Bloody stools with fever and systemic toxicity 5
• Persistent vomiting despite small-volume ORS administration 5
• Signs of shock 1

Important Differential Diagnoses

Fever, vomiting, and loose stools can indicate many non-gastrointestinal illnesses including meningitis, bacterial sepsis, pneumonia, otitis media, and urinary tract infection 4. A detailed history and physical examination are essential 4.

Investigation

Clinical Assessment (Primary)

• Obtain accurate body weight - acute weight change is the most accurate assessment of fluid status if premorbid weight is known 5
• Auscultate for adequate bowel sounds before initiating oral therapy 1
• Assess skin turgor, mental status, mucous membrane moisture, capillary refill, and vital signs 5

Laboratory Testing (Selective, Not Routine)

Most cases do not require laboratory testing 3. Reserve investigations for:

Indications for Stool Studies

• Bloody diarrhea or white blood cells on methylene blue stain - perform stool cultures 4
• Recent antibiotic use (suspect Clostridium difficile) 4
• Exposure to day care centers where Giardia or Shigella is prevalent 4
• Recent foreign travel 4
• Immunodeficiency 4
• Prolonged or complicated cases 6

Blood Tests

• Complete blood count and acute phase reactants only in patients with signs of severe disease 6
• Blood cultures if febrile or toxic-appearing 5

Common pitfall: Delaying rehydration therapy while awaiting diagnostic testing is not recommended; rehydration should be initiated promptly 5.

Management

Rehydration Therapy (Cornerstone of Treatment)

Mild to Moderate Dehydration (First-Line: Oral Rehydration)

Oral rehydration solution (ORS) is the first-line treatment for mild to moderate dehydration 1, 5. This approach successfully rehydrates >90% of children with vomiting and diarrhea 5.

Administration technique (critical for success):

• Begin with 5-10 mL every 1-2 minutes using a spoon or syringe 1, 5
• Gradually increase volume as tolerated without triggering vomiting 5
• Low-osmolarity ORS formulations are preferred over sports drinks or juices 1

Dosing for moderate dehydration (6-9% deficit):

• Administer 100 mL/kg ORS over 2-4 hours 5
• Replace ongoing losses: 10 mL/kg ORS for each watery stool and 2 mL/kg for each vomiting episode 5
• Reassess hydration status after 2-4 hours 5

Alternative route: Nasogastric administration of ORS may be considered for patients who cannot tolerate oral intake or refuse to drink adequately 5.

Severe Dehydration (Intravenous Rehydration Required)

Reserve intravenous rehydration for patients with severe dehydration (≥10% fluid deficit), shock, altered mental status, failure of oral rehydration therapy, or ileus 1, 5.

• Use isotonic fluids such as lactated Ringer's or normal saline 5
• Continue IV rehydration until pulse, perfusion, and mental status normalize 5
• Transition to ORS to replace remaining deficit once patient improves 5

Nutritional Management

Breastfeeding

Continue breastfeeding immediately after rehydration 4. Breastfeeding should continue throughout the diarrheal episode 5.

Formula-Fed Infants

• Resume regular formula immediately during or after rehydration 5
• Early refeeding is recommended rather than fasting or restrictive diets 5
• Avoid prolonged use of diluted formulas, which results in inadequate energy and protein content 4

Older Children

Resume age-appropriate diet immediately during or after rehydration 5, 7. Recommended foods include:

• Starches: rice, potatoes, noodles, crackers, bananas 4, 7
• Cereals: rice, wheat, oat cereals 4, 7
• Soup, yogurt, vegetables, fresh fruits 4, 7

Foods to avoid:

• Foods high in simple sugars (soft drinks, undiluted apple juice, Jell-O, presweetened cereals) - exacerbate diarrhea by osmotic effects 4
• High-fat foods - may delay gastric emptying 4
• Caffeinated beverages - can worsen symptoms through stimulation of intestinal motility 5

Common pitfall: Prolonged use of the "BRAT diet" (bananas, rice, applesauce, toast) can result in inadequate energy and protein content 4.

Pharmacologic Management

Antimicrobial Therapy (Limited Role)

Since viral agents are the predominant cause of acute diarrhea, antimicrobial agents play only a limited role 4.

Indications for antimicrobial therapy:

• Bloody diarrhea with bacterial pathogen identified on culture 4
• Infants <3-6 months with suspected bacterial AGE 6
• Patients with underlying disease or signs of sepsis 6
• Immunodeficiency 4
• Institutionalized patients or settings with risk of dissemination 6

Specific pathogens:

• Non-Typhi Salmonella and STEC: targeted antibiotherapy restricted to patients at risk of systemic infection or with prolonged diarrhea 6
• Shigella: consider antimicrobials in day care settings 4
• Clostridium difficile: in patients with recent antibiotic use 4

Antiemetics

Ondansetron may be given to children >4 years and adolescents to facilitate oral rehydration when vomiting is significant 5. For younger children with vomiting, administer small volumes of ORS (5-10 mL) every 1-2 minutes 7.

Probiotics

Probiotics may reduce symptom severity and duration in both adults and children 5. Specific strains with documented efficacy include Lactobacillus rhamnosus GG, Lactobacillus reuteri, and Saccharomyces boulardii 3.

Zinc Supplementation

Zinc supplementation reduces diarrhea duration in children 6 months to 5 years of age in areas with high zinc deficiency prevalence or in children with signs of malnutrition 5.

Medications to AVOID

Antimotility agents (loperamide) should NOT be given to children <18 years with acute diarrhea 5. Serious adverse events including ileus and deaths have been reported, with 18 cases of severe abdominal distention and at least 6 deaths documented in Pakistan 4.

Nonspecific antidiarrheal agents (adsorbents like kaolin-pectin, antisecretory drugs, toxin binders like cholestyramine) should be avoided:

• Do not demonstrate effectiveness in reducing diarrhea volume or duration 4
• Stool water losses are unchanged and electrolyte losses may increase 4
• Side effects include opiate-induced ileus, drowsiness, nausea 4
• Shifts therapeutic focus away from appropriate fluid, electrolyte, and nutritional therapy 4

Metoclopramide should NOT be used in gastroenteritis management - it is counterproductive as it increases gastrointestinal motility 5.

Infection Control Measures

Practice proper hand hygiene after using toilet or changing diapers, before and after food preparation, before eating, and after handling soiled items 1, 5.

Additional measures:

• Use gloves and gowns when caring for children with diarrhea 5
• Clean and disinfect contaminated surfaces promptly 1, 5
• Separate ill persons from well persons until at least 2 days after symptom resolution 1, 5

Prevention

Rotavirus Vaccination

Two FDA-licensed rotavirus vaccines are recommended by ACIP: RotaTeq (RV5) and Rotarix (RV1) 1. These vaccines have demonstrated good safety and efficacy profiles in large clinical trials 3.

Home Management Education

Families should keep ORS at home at all times and begin administration when diarrhea first occurs, before seeking medical care 5. Caregivers must be instructed on:

• Small-volume, frequent administration technique (5-10 mL every 1-2 minutes) 5
• Warning signs requiring return to medical care 5

Hospitalization Criteria

Admit patients with:

• Severe dehydration (≥10% fluid deficit) 1, 5
• Signs of shock 1, 5
• Failure of oral rehydration therapy 1, 5
• Altered mental status 1, 5
• Intractable vomiting despite antiemetics 5
• Significant comorbidities that increase risk of complications 5

Special populations requiring lower threshold for admission:

• Infants <3 months - higher risk of severe dehydration and complications 1, 5
• Immunocompromised patients 5

Monitoring and Follow-Up

Monitor vital signs every 2-4 hours, including:

• Capillary refill 1, 5
• Skin turgor 1, 5
• Mental status 1, 5
• Mucous membrane moisture 1, 5

Daily weights should be tracked to monitor rehydration progress 1, 5.

Plan discharge when: tolerating oral intake, producing urine, and clinically rehydrated 1, 5.

Special Considerations for Infants <6 Months

• Higher risk of severe dehydration due to higher body surface-to-weight ratio and higher metabolic rate 5
• Lower threshold for hospitalization given increased vulnerability 1, 5
• Continue breastfeeding throughout illness 4, 5
• Consider milk protein allergy if symptoms persist - trial extensively hydrolyzed protein or amino acid-based formula for 2-4 weeks 7
• Empirical antibiotherapy may be indicated in infants <3-6 months with suspected bacterial AGE 6