Acute Gastroenteritis in Children: Comprehensive Lecture Notes
Definition and Classification
Acute gastroenteritis is defined as acute onset of vomiting and/or diarrhea, typically lasting less than 7 days, with diarrhea characterized by increased frequency and decreased consistency of stools. 1
Duration categories:
Clinical presentation: After 1-3 day incubation, acute onset of fever and vomiting occurs, followed 24-48 hours later by watery diarrhea, with typically 10-20 bowel movements per day 1
Epidemiology
Acute gastroenteritis is the second most common non-traumatic cause of emergency hospitalization in children aged 1-5 years, accounting for approximately 9% of cases. 2
United States Burden (Pre-Rotavirus Vaccine Era)
- Nearly every child infected by age 5 years 1
- Annual burden: 179 million outpatient visits, nearly 500,000 hospitalizations, >5,000 deaths 1
- In first 5 years of life: 4 of 5 children develop rotavirus gastroenteritis, 1 in 7 require clinic/ED visit, 1 in 70 hospitalized, 1 in 200,000 die 1
Post-Vaccine Era Changes
- Rotavirus vaccine implementation (2006-2008) significantly reduced disease burden through both direct and indirect (community) protection 1
- Norovirus has now assumed the lead as most common pathogen in children <5 years, causing nearly 1 million ambulatory care visits and 14,000 hospitalizations annually 1
Age-Specific Patterns
- Disease incidence highest among children <5 years 1
- Severe, dehydrating gastroenteritis occurs primarily in children 3-35 months of age 1
- Infants are particularly vulnerable due to higher body surface-to-weight ratio, higher metabolic rate, and dependence on caregivers for fluid intake 1
Etiology
Viral Pathogens (Most Common)
Viruses account for the majority of acute gastroenteritis cases, with four main families responsible: rotaviruses, caliciviruses (including norovirus), astroviruses, and enteric adenoviruses. 3, 4
- Norovirus: Most common pathogen in hospitalized children (27% in recent studies), responsible for 58% of gastroenteritis illnesses overall 1, 5
- Rotavirus: Second most common (21% in hospitalized children), though previously the leading cause before vaccine introduction 5
- Enteric adenoviruses: 14% of viral gastroenteritis cases 2
- Astroviruses: Less common but significant contributor 2, 3
Bacterial Pathogens
The five most common bacterial pathogens in children <5 years are Salmonella enterica subspecies (42%), Campylobacter (28%), Shigella (21%), Yersinia (5%), and E. coli O157 (3%). 1
- Together cause an estimated 291,000 illnesses, 103,000 physician visits, 7,800 hospitalizations, and 64 deaths yearly 1
- Salmonella enterica subspecies accounts for 35% of hospitalizations and 28% of deaths from gastroenteritis pathogens 1
Transmission Patterns
- Fecal-oral route: Primary transmission mechanism 1
- Children shed >100 billion virus particles per gram of stool during acute illness 1
- Shedding may occur before symptom development and persist up to 10 days after symptom onset 1
- Spread within families is common: 30-50% of adult contacts become infected, though most remain asymptomatic 1
- Important cause of hospital-acquired diarrhea and major cause in childcare settings 1
Seasonal Patterns (Rotavirus)
- Yearly epidemics from late fall to early spring in United States 1
- Peak begins in Southwest (November-December), travels west to east, concluding in Northeast (April-May) 1
Clinical Manifestations
Typical Presentation
Gastroenteritis begins with acute onset of fever and vomiting, followed 24-48 hours later by watery diarrhea, with symptoms generally persisting 3-8 days. 1
- Vomiting: Nonbilious, occurs in 80-90% of infected children, usually lasts <24 hours 1
- Diarrhea: Watery consistency, typically 10-20 bowel movements per day 1
- Fever: Occurs in up to half of infected children, usually low-grade, though up to one-third may have temperature >39°C 1
Severity Spectrum
- Clinical spectrum ranges from mild, watery diarrhea of limited duration to severe diarrhea with vomiting and fever that can result in dehydration with shock, electrolyte imbalance, and death 1
- Rotavirus infection results in more severe disease than other gastroenteritis pathogens, accounting for higher proportion of severe episodes requiring outpatient or hospital visits 1
Complications
- Lactose intolerance: Observed in 7.5% of cases, most commonly due to rotavirus infection 5
- Seizures: Reported in some children with severe gastroenteritis 5
- Dehydration: Primary cause of morbidity and mortality 1
Diagnosis and Clinical Assessment
Initial Evaluation
A detailed history and physical examination are essential, as fever, vomiting, and loose stools can indicate many nongastrointestinal illnesses including meningitis, bacterial sepsis, pneumonia, otitis media, and urinary tract infection. 1
- Accurate body weight must be obtained 1
- Auscultate for adequate bowel sounds before initiating oral therapy 1
- Visual examination of stool to confirm abnormal consistency and determine presence of blood or mucus 1
Dehydration Assessment
The most accurate assessment of fluid status is acute weight change, though premorbid weight is often unknown. 1, 6
Mild Dehydration (3-5% fluid deficit)
Moderate Dehydration (6-9% fluid deficit)
Severe Dehydration (≥10% fluid deficit)
- Severe lethargy or altered state of consciousness 1, 6
- Prolonged skin tenting and skin retraction time (>2 seconds) 1, 6
- Cool and poorly perfused extremities 1, 6
- Decreased capillary refill 1, 6
- Rapid, deep breathing (sign of metabolic acidosis) 1, 6
Prolonged skin retraction time and rapid deep breathing are more reliably predictive of significant dehydration than sunken fontanelle or absence of tears. 6
Laboratory Investigation
Most acute diarrhea episodes in previously healthy, immunocompetent children are self-resolving and of viral or unknown etiology; therefore, laboratory investigation generally is not warranted. 1
Indications for Testing
Laboratory testing may be justified when:
- Bloody diarrhea present 1, 6
- Recent antibiotic use (suspect Clostridium difficile) 1
- Exposure to childcare centers where Giardia or Shigella is prevalent 1
- Recent foreign travel 1
- Immunodeficiency 1
- Suspicion of outbreak situation 1
Specific Tests
- Stool cultures: If bloody diarrhea or white blood cells on methylene blue stain present 7
- Urinalysis with microscopy and urine culture: To rule out UTI/pyelonephritis when urinary symptoms or abdominal pain present 6
- Blood cultures: If febrile or toxic-appearing 6
Treatment
Oral Rehydration Therapy (First-Line Treatment)
The American Academy of Pediatrics and Centers for Disease Control and Prevention recommend oral rehydration solution (ORS) as the first-line treatment for mild to moderate dehydration in children. 6
ORS Administration Technique
- Use small, frequent volumes (5-10 mL every 1-2 minutes via spoon or syringe) to prevent triggering more vomiting, gradually increasing as tolerated 6, 7
- This technique successfully rehydrates >90% of children with vomiting and diarrhea without any antiemetic medication 6
- Low-osmolarity ORS formulations are preferred over sports drinks or juices 6
Dosing by Dehydration Severity
- Mild dehydration (3-5%): 50 mL/kg ORS over 2-4 hours 6, 7
- Moderate dehydration (6-9%): 100 mL/kg ORS over 2-4 hours 6, 7
- Replace ongoing losses: 10 mL/kg ORS for each watery stool, 2 mL/kg for each vomiting episode 6, 7
- Reassess hydration status after 2-4 hours; if still dehydrated, reestimate deficit and restart rehydration 6
Alternative Route
- Nasogastric administration of ORS may be considered for patients who cannot tolerate oral intake or refuse to drink adequately 6
- Continuous nasogastric application is just as effective as intravenous rehydration and is the treatment of first choice for children who are vomiting or refuse oral ORS 2
Evidence Base
In 17 randomized controlled trials involving 1,811 children with mild or moderate dehydration, oral rehydration was just as effective as intravenous rehydration regarding weight gain, duration of diarrhea, and fluid administration, and was associated with shorter hospital stays (weighted mean difference -1.2 days) 2
Intravenous Rehydration
Reserve intravenous rehydration for patients with severe dehydration (≥10% fluid deficit), shock, altered mental status, failure of oral rehydration therapy, or ileus. 6, 7
- Use isotonic fluids: Lactated Ringer's or normal saline 6, 7
- Continue IV rehydration until pulse, perfusion, and mental status normalize 6
- Transition to ORS to replace remaining deficit once patient improves 6
Nutritional Management
Resume age-appropriate diet during or immediately after rehydration; early refeeding is recommended rather than fasting or restrictive diets. 6, 7
- Continue breastfeeding in infants throughout the diarrheal episode 6
- Offer starches (rice, potatoes, noodles, crackers, bananas), cereals (rice, wheat, oat), soup, yogurt, vegetables, and fresh fruits 7
- Avoid foods high in simple sugars (soft drinks, undiluted apple juice, Jell-O, presweetened cereals) as they exacerbate symptoms through osmotic effects 6, 7
- Avoid high-fat foods as they may delay gastric emptying and worsen tolerance 7
- Limit or avoid caffeine as it can exacerbate symptoms through stimulation of intestinal motility 6
- Early refeeding reduces severity and duration of illness 6, 7
Pharmacological Management
Antiemetics
Ondansetron may be given to children >4 years and adolescents to facilitate oral rehydration when vomiting is significant. 6
- Typical dose: 0.15 mg/kg orally dissolving tablet 8
Antimotility Agents
Loperamide should NOT be given to children <18 years with acute diarrhea. 6, 7
- Serious adverse events including ileus, drowsiness, and deaths have been reported 1, 6, 8
- One report from Pakistan detailed 18 cases of severe abdominal distention with loperamide use, including at least six deaths 1
Other Agents to Avoid
The use of nonspecific antidiarrheal agents such as adsorbents (kaolin-pectin), antisecretory drugs, or toxin binders (cholestyramine) is not recommended. 1, 6
- Available data do not demonstrate effectiveness in reducing diarrhea volume or duration 1
- Side effects are well known and reliance on these agents shifts therapeutic focus away from appropriate fluid, electrolyte, and nutritional therapy 1, 6
Probiotics
Probiotics may reduce symptom severity and duration in both adults and children. 6
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. 6
Antimicrobial Therapy
Antimicrobial agents have limited usefulness in management of acute gastroenteritis since viral agents are the predominant cause. 6, 7
Antimicrobial therapy should be considered only in specific cases:
- Bloody diarrhea with fever and systemic toxicity 6, 7
- Recent antibiotic use (suspect C. difficile) 1, 7
- Exposure to childcare centers where Giardia or Shigella is prevalent 1, 7
- Recent foreign travel 1, 7
- Immunodeficiency 1, 7
Prevention
Vaccination
Two FDA-licensed rotavirus vaccines are recommended by ACIP: RotaTeq (RV5) administered in 3-dose series at 2,4, and 6 months, and Rotarix (RV1) administered in 2-dose series at 2 and 4 months. 1
Vaccine Efficacy
- 98% efficacy for prevention of severe rotavirus illness 1
- 74% efficacy for prevention of rotavirus-induced diarrheal episodes of any severity 1
- Immunization early in life mimics a child's first natural infection and will not prevent all subsequent disease but should prevent most cases of severe rotavirus 1
Rationale for Vaccination
- Clean water supplies and good hygiene have little effect on virus transmission, so improvements in water or hygiene are unlikely to prevent disease 1
- Rate of hospitalizations for gastroenteritis in young children declined only 16% from 1979-1995 despite widespread recommendation for oral rehydration solutions 1
- Natural rotavirus infection protects against subsequent severe gastroenteritis 1
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. 6
- Use gloves and gowns when caring for people with diarrhea 6
- Clean and disinfect contaminated surfaces promptly 6, 7
- Separate ill persons from well persons until at least 2 days after symptom resolution 6
General Preventive Measures
- Avoidance of high-risk foods such as undercooked meat and seafood, unpasteurized milk, and soft cheese made with unpasteurized milk 1
- Avoidance of unsafe water 1
- Use of infection prevention and control measures in hospitals, childcare, and nursing facilities 1
Hospitalization Criteria
Admit patients with severe dehydration (≥10% fluid deficit), signs of shock, failure of oral rehydration therapy, altered mental status, intractable vomiting despite antiemetics, or significant comorbidities that increase risk of complications. 6, 8, 7
High-Risk Populations Requiring Lower Threshold
- Infants <3 months warrant careful consideration for admission given higher risk of severe dehydration and complications 6
- Immunocompromised patients (including those on immunosuppressive therapy, HIV-infected, transplant recipients, or with malignancy) due to risk of severe or prolonged illness 6
Specific Clinical Presentations
- Bloody diarrhea with fever and systemic toxicity may indicate dysentery requiring hospitalization for monitoring of complications like hemolytic uremic syndrome 6
- Severe abdominal pain disproportionate to examination findings or suggesting surgical abdomen requires hospitalization 6
- Absent bowel sounds on auscultation is an absolute contraindication to oral rehydration 6
Critical Red Flags Requiring Immediate Attention
Severe dehydration (≥10% fluid deficit) constitutes a medical emergency requiring immediate intravenous rehydration. 6
Signs of Severe Dehydration
- Severe lethargy or altered consciousness 6
- Prolonged skin tenting (>2 seconds) 6
- Cool and poorly perfused extremities 6
- Decreased capillary refill 6
- Rapid, deep breathing indicating metabolic acidosis 6
Other Critical Red Flags
- Bloody stools with fever and systemic toxicity may indicate bacterial infection requiring immediate medical evaluation and stool culture 6
- Persistent vomiting despite small-volume ORS administration (5-10 mL every 1-2 minutes) indicates failure of oral rehydration therapy 6
- Absent bowel sounds on auscultation; oral fluids should not be given until bowel sounds return 6
- Stool output >10 mL/kg/hour is associated with lower success rates of oral rehydration, though ORT should still be attempted 6
Common Pitfalls to Avoid
Do not delay rehydration therapy while awaiting diagnostic testing; rehydration should be initiated promptly. 6, 7
- Do not use inappropriate fluids like apple juice or sports drinks as primary rehydration solutions for moderate to severe dehydration 6, 7
- Do not administer antimotility drugs to children or in cases of bloody diarrhea 6, 7
- Do not unnecessarily restrict diet during or after rehydration 6, 7
- Do not rely on the "BRAT diet" exclusively (bananas, rice, applesauce, toast) for prolonged periods, as it provides inadequate energy and protein 7
- Do not use diluted formulas for extended periods, as this results in inadequate nutrition 7
- Do not neglect infection control measures as this can lead to outbreaks 6
- Do not underestimate dehydration in infants, who may not manifest classic signs and have higher risk of complications 6
Monitoring and Follow-Up
Monitor vital signs every 2-4 hours, including capillary refill, skin turgor, mental status, and mucous membrane moisture, to assess for signs of worsening dehydration or progression to severe dehydration. 6
- Daily weights to track rehydration progress 6
- Plan discharge when: tolerating oral intake, producing urine, clinically rehydrated 6
Family Education
- Families should keep ORS at home at all times and begin administration when diarrhea first occurs, before seeking medical care 6
- Provide clear instructions on small-volume, frequent administration technique (5-10 mL every 1-2 minutes via spoon or syringe) 6, 7
- Educate on warning signs requiring return to medical care: decreased urine output, lethargy or irritability, high fever, bloody stools, persistent vomiting 6