Pediatric Gastroenteritis (Acute Infectious Diarrhea)

Pediatric gastroenteritis is a leading cause of morbidity and mortality in children under 5, primarily because of dehydration. This note reviews the causes, pathophysiology, clinical assessment, and evidence-based management (including WHO rehydration plans) that nursing students must master for both practice and exams.

Definition

• Gastroenteritis is acute inflammation of the stomach and intestines causing diarrhea with or without vomiting.
• Usually caused by infectious agents: viruses, bacteria, or parasites.
• One of the leading causes of morbidity and mortality in children under 5 years, mainly due to dehydration.

Etiology

• Viral (most common): Rotavirus (most important in infants), Norovirus, Adenovirus — watery diarrhea; self-limiting.
• Bacterial: E. coli (ETEC, EPEC, EHEC), Shigella, Salmonella, Campylobacter, Vibrio cholerae — bloody diarrhea (except cholera); fever common.
• Parasitic: Giardia, Entamoeba histolytica — prolonged symptoms.

Key points:

• Rotavirus is the most common cause of severe gastroenteritis in infants; the rotavirus vaccine has significantly reduced its incidence.
• Norovirus is the most common cause in older children and adults and is highly contagious.
• EHEC can cause hemolytic uremic syndrome (HUS), a life-threatening complication.
• Cholera causes profuse, watery diarrhea ("rice water stools") and rapid severe dehydration.

Pathophysiology

Non-inflammatory (Secretory / Watery Diarrhea)

• Caused by viral infection or enterotoxin-producing bacteria (Vibrio cholerae, ETEC).
• No invasion of the intestinal mucosa.
• Toxins activate adenylate cyclase → ↑ cAMP → chloride secretion, and water follows.
• Result: watery diarrhea without blood or pus.

Inflammatory (Dysentery)

• Caused by mucosal invasion from Shigella, Salmonella, Campylobacter, EHEC.
• Direct invasion → inflammation, ulceration, and bleeding.
• Result: blood, mucus, and pus in the stool.
• Fever and abdominal pain are prominent.

Osmotic Diarrhea

• Caused by malabsorption of carbohydrates (e.g., lactose intolerance, rotavirus).
• Undigested sugars draw water into the intestinal lumen.
• Stool pH <5.5 and reducing substances present.

Clinical Features

• Acute onset diarrhea is the hallmark.
• Vomiting often occurs early, especially in viral cases.
• Fever is variable; may be high in bacterial infections.
• Stool characteristics help differentiate the cause:
  • Watery → viral, secretory, or osmotic
  • Bloody → bacterial dysentery
  • Rice water → cholera
  • Foul-smelling, greasy → malabsorption or Giardia

Dehydration Assessment

• Weight loss is the most accurate indicator of dehydration.
• Mild: thirst only; child appears well.
• Moderate: sunken eyes, reduced tears, tachycardia, decreased skin turgor.
• Severe: medical emergency — lethargy, very sunken eyes, hypotension, shock, minimal urine output.

Red Flags

• Persistent vomiting preventing oral fluid tolerance
• High fever >39°C
• Bloody diarrhea
• Lethargy or altered mental status
• Signs of severe dehydration or shock
• No urine output for more than 6–8 hours

Investigations

• Clinical diagnosis is usually sufficient.
• Stool examination in severe or persistent cases:
  • WBC → inflammatory diarrhea
  • RBC → invasive dysentery
  • Stool culture → identifies bacterial pathogens
• Check electrolytes in dehydration.
• Check blood glucose in infants (risk of hypoglycemia).

Management

Rehydration Therapy

ORS (Oral Rehydration Solution) — First Line

• Used for mild to moderate dehydration.
• Contains glucose and sodium to promote absorption via SGLT1.
• WHO-ORS composition: Sodium 75 mEq/L, Potassium 20 mEq/L, Chloride 65 mEq/L, Citrate 10 mmol/L, Glucose 75 mmol/L.
• Breastfeeding should continue.

WHO ORS Plans

• Plan A (No dehydration): ORS after each loose stool.
  • <2 years: 50–100 mL
  • ≥2 years: 100–200 mL
• Plan B (Some dehydration): ORS 75 mL/kg over 4 hours; reassess every 1–2 hours.
• Plan C (Severe dehydration): IV fluids immediately.

IV Fluids

• Indications: severe dehydration, shock, persistent vomiting.
• Fluid of choice: Ringer's lactate or normal saline.
• Severe dehydration:
  • <1 year: 100 mL/kg over 6 hours

  • 1 year: 30 mL/kg over 30–60 minutes

• Shock: 20 mL/kg rapid bolus, repeat if needed.

Zinc Supplementation (WHO Recommendation)

• Reduces duration, severity, and recurrence of diarrhea.
• <6 months: 10 mg/day for 10–14 days.
• >6 months: 20 mg/day for 10–14 days.

Diet

• Continue feeding during diarrhea — do not stop food.
• Breastfeeding must continue.
• Avoid high-sugar drinks (soda, juice) — worsen diarrhea.

Antibiotics (Only if Indicated)

• Antibiotics are not used for viral gastroenteritis.
• EHEC should not be treated with antibiotics due to risk of HUS.

Hemolytic Uremic Syndrome (HUS)

• Life-threatening complication of EHEC infection, especially O157:H7.
• Classic triad: acute renal failure, hemolytic anemia, thrombocytopenia.
• Clinical features: pallor, fatigue, oliguria/anuria, bruising, petechiae.
• Management: supportive care, dialysis, blood transfusions.
• Prevention: avoid antibiotics for EHEC.

Complications

• Severe dehydration → shock
• Electrolyte imbalances (hyponatremia, hypokalemia, metabolic acidosis)
• Hypoglycemia in infants
• Malnutrition
• Hemolytic uremic syndrome (HUS)
• Death if untreated

Prevention

• Rotavirus vaccine — the most important preventive measure.
• Hand hygiene prevents transmission.
• Safe drinking water and proper sanitation.
• Exclusive breastfeeding for the first 6 months.
• Proper food hygiene prevents bacterial contamination.

Clinical Differentiation

Key Takeaways

• The most common cause in infants is Rotavirus; the most common cause of death is dehydration.
• ORS is first-line treatment; IV fluids are reserved for severe dehydration or shock.
• Do not stop feeding during diarrhea — continue breastfeeding.
• Zinc supplementation (10 mg <6 mo, 20 mg ≥6 mo for 10–14 days) reduces duration and recurrence.
• Avoid antibiotics in EHEC to prevent HUS (acute renal failure + hemolytic anemia + thrombocytopenia).
• Weight loss is the most accurate indicator of dehydration; lethargy, sunken eyes, and anuria signal a medical emergency.