Acute diarrheal disease in pediatrics

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Acute Diarrheal Disease in Pediatrics

Definition

Acute diarrhea is defined as a change in bowel habits with increased stool frequency (>3 loose stools/day) or decreased consistency, lasting less than 14 days. It is one of the most common pediatric complaints worldwide and contributes to >500,000 deaths annually in children under 5 years of age globally.

Tintinalli's Emergency Medicine, Ch. 31
ROSEN's Emergency Medicine, Ch. 167

Etiology

Common Causes by Pathogen Category

Viruses (70-80%)	Bacteria (10-20%)	Protozoa (<10%)
Rotavirus	Salmonella spp.	Cryptosporidium
Norovirus / Sapovirus	Shigella spp.	Giardia intestinalis
Astrovirus	Campylobacter jejuni	Entamoeba histolytica
Adenovirus	Yersinia enterocolitica
	ETEC, STEC (O157:H7)
	C. difficile, S. aureus
	Vibrio cholerae

Rotavirus was previously the leading cause of severe pediatric diarrhea. Since introduction of the RotaTeq (RV5, 2006) and Rotarix (RV1, 2008) vaccines in the US, hospitalizations and ED visits have declined by 60-90%, averting an estimated 177,000 hospitalizations and 242,000 ED visits. Norovirus is now the pathogen responsible for the greatest burden of medically attended gastroenteritis in immunized populations.

ROSEN's Emergency Medicine, p. 3228-3232

Non-infectious Causes to Consider

Antibiotic-associated diarrhea / C. difficile
Dietary indiscretion or intolerance (lactose, fructose)
Inflammatory bowel disease (IBD) - especially in older children
Intussusception, malrotation, Hirschsprung's disease (in neonates/infants)
Systemic illness (sepsis, urinary tract infection)
Medications / toxins

Pathophysiology

Four main mechanisms:

Secretory - pathogens (e.g., ETEC, cholera) produce enterotoxins that activate adenylate/guanylate cyclase, increasing cAMP/cGMP → massive Cl⁻ and water secretion. Stool is large-volume, watery, non-bloody.
Osmotic - unabsorbed solutes draw water into the lumen (e.g., viral damage to brush border, lactase deficiency). Stops with fasting.
Invasive/inflammatory (dysentery) - organisms (Shigella, Salmonella, Campylobacter, EHEC) invade and destroy mucosa → bloody/mucoid stool, fever, fecal WBCs.
Motility-related - altered transit time (less common in children).

Clinical Assessment

History

Key points to elicit:

Onset, frequency, character (watery, bloody, mucoid), duration
Associated vomiting, fever, abdominal pain
Food history, water source, recent camping/travel to endemic areas
Similar illness in household contacts or school
Recent antibiotic use
Vaccination history (rotavirus)
Chronic medical problems

Physical Examination - Dehydration Assessment

The Clinical Dehydration Scale (CDS) and Gorelick Scale are validated tools:

Clinical Dehydration Scale (CDS)

Feature	0	1	2
General appearance	Normal	Thirsty, restless, or lethargic but irritable	Drowsy, limp, cold, sweaty, or comatose
Eyes	Normal	Slightly sunken	Very sunken
Mucous membranes	Moist	Sticky	Dry
Tears	Present	Decreased	Absent

Score 0 = No dehydration (<3%)
Score 1-4 = Some dehydration (3-6%)
Score 5-8 = Moderate-severe dehydration (≥6%)

Gorelick Scale (10-point):

3 or more signs = ≥5% dehydration
7 or more signs = ≥10% dehydration

Key signs: capillary refill time, skin turgor (slow recoil >2 sec = severe), quality of pulses, respiratory pattern, urine output, heart rate, and mental status.

Red Flag Signs (Indications for Immediate Medical Evaluation):

Bloody/mucoid stool (dysentery pattern)
High fever (>38.5°C in infants <3 months)
Signs of moderate-severe dehydration or shock
Persistent vomiting preventing ORT
Ill-appearing or lethargic child
Immunocompromised child
Age < 3 months
ROSEN's Emergency Medicine, BOX 167.3

Diagnostic Workup

Laboratory Tests

Routine labs have low yield in mild-moderate cases. Consider in:

Moderate-severe dehydration: electrolytes, BUN, creatinine, blood glucose
Serum bicarbonate >15 mEq/L makes significant dehydration unlikely
BUN is elevated in severe dehydration but poorly discriminates mild cases

Stool Studies

Routine stool cultures are not recommended - diagnostic yield as low as 2%. Indications for stool culture:

10 stools in prior 24 hours
Travel to high-risk country
Fever with bloody or mucoid stools
Persistent diarrhea (>7-14 days)
Suspicion of inflammatory bowel disease
Immunocompromised host
Stool E. coli O157 serotyping if HUS is suspected

Fecal leukocytes / fecal lactoferrin: >5 WBCs per HPF has sensitivity 73%, specificity 84% for bacterial etiology. Lactoferrin is a better and more practical marker.

Multiplex PCR stool panels can rapidly identify viral, bacterial, and parasitic pathogens simultaneously and are increasingly used in clinical practice.

Imaging

Radiologic studies play a very limited role. Plain films may be used when obstruction, foreign body, or perforation is suspected. Ultrasound is valuable to exclude intussusception or appendicitis.

Tintinalli's Emergency Medicine, p. 888

Management

1. Oral Rehydration Therapy (ORT) - First Line

ORT is the cornerstone of treatment for mild-to-moderate dehydration. It exploits the sodium-glucose cotransport mechanism on the intestinal brush border (remains intact even in severe diarrhea, functioning optimally at a Na:glucose ratio of 1:1).

WHO Reduced-Osmolarity ORS (2002): Na 75 mmol/L, glucose 75 mmol/L, K 20 mmol/L, Cl 65 mmol/L, citrate 10 mmol/L → osmolarity 245 mOsm/L

Solution	Na (mmol/L)	Glucose (mmol/L)	Osmolarity (mOsm/L)
WHO reduced-osmolarity ORS	75	75	245
Pedialyte®	45	139	250
Apple juice	~3	~690	~700
Sports drinks	~20	~255	~330

Apple juice, sports drinks, and clear sodas are not appropriate rehydration solutions due to excessive sugar and insufficient sodium - they can worsen osmotic losses. Exception: in high-income countries, dilute apple juice followed by preferred fluids is an acceptable alternative in children with minimal dehydration (CDS ≤4, capillary refill <2 sec).

ORT Protocol (Mild-Moderate Dehydration):

Estimate degree of dehydration (mild 3-5%, moderate 6-9%)
Calculate fluid deficit: 30-50 mL/kg for mild; 60-80 mL/kg for moderate
Replace 25% of calculated deficit each hour over 4 hours
Replace ongoing losses: 10 mL/kg per stool, 2 mL/kg per emesis
Resume normal feeding after rehydration phase

Cochrane review: ORT vs. IV therapy shows no difference in rehydration failure or weight gain; ORT is associated with a shorter hospital stay. For every 25 children treated with ORT, one will fail and require IV fluids.

ROSEN's Emergency Medicine, p. 3553-3565
Tintinalli's Emergency Medicine, p. 370-371

2. IV Rehydration - Indications

Reserve IV fluids for:

Severe dehydration (≥10%, signs of shock)
Hemodynamic compromise
Altered mental status (unable to take oral fluids safely)
Persistent vomiting refractory to ORT
Suspected intestinal obstruction or acute abdomen
Significant electrolyte abnormalities (severe hypo/hypernatremia)

IV bolus: 20 mL/kg isotonic saline (0.9% NaCl or Lactated Ringer's), repeat as needed. Continue ORT alongside IV therapy once tolerated.

3. Antiemetics

Ondansetron (5-HT3 antagonist) is the antiemetic of choice in children with gastroenteritis-associated vomiting. It improves ORT tolerance and reduces IV fluid requirements.

Dosing: 0.15-0.3 mg/kg PO/IV (max 4-8 mg), single dose in most cases

4. Antibiotic Therapy

Antibiotics are not indicated routinely. Most viral and self-limited bacterial diarrheas do not benefit. Indications and regimens:

Organism	Routine Treatment	High-Risk / Invasive Disease
Salmonella (non-typhoidal)	No - prolongs excretion	High-risk patients (infants <3 mo, immunocompromised, hemoglobinopathy): Ceftriaxone 50-75 mg/kg/day or Ciprofloxacin 20-40 mg/kg/day (max 1 g/day)
Salmonella typhi (enteric fever)	All patients require treatment	Ceftriaxone 50-75 mg/kg q24h (max 2 g) or Ciprofloxacin IV/PO; multidrug resistance is common
Shigella	Self-limited but treatment decreases duration and clears organism	Ceftriaxone 50 mg/kg/day x5 days; Azithromycin 20 mg/kg/day (max 500 mg); TMP-SMX if susceptible
Campylobacter	Usually self-limited	Azithromycin 10-20 mg/kg/day x3-5 days for severe/immunocompromised
STEC (E. coli O157:H7)	Antibiotics contraindicated - may increase HUS risk	Supportive care; IV fluids for hemorrhagic colitis
Giardia	Metronidazole 15 mg/kg/day TID x5-7 days	Tinidazole (single dose) or Nitazoxanide
Cryptosporidium	Nitazoxanide in immunocompetent children
C. difficile	Oral Metronidazole or Vancomycin	Fidaxomicin for recurrence

ROSEN's Emergency Medicine, TABLE 167.4

5. Diet and Feeding

Do not restrict diet - early refeeding reduces intestinal permeability and promotes mucosal repair
Lactose restriction is generally not needed; most children tolerate lactose during acute illness
Breastfeeding should continue throughout illness
BRAT diet (Bananas, Rice, Applesauce, Toast) is no longer recommended as the sole diet - it is nutritionally inadequate
Avoid high-fat foods and high-osmolarity drinks

6. Adjunctive Therapies

Probiotics: A 2025 meta-analysis (PMID 40739406) confirms reduction in duration and severity of acute gastroenteritis in children. Lactobacillus rhamnosus GG and Saccharomyces boulardii have the best evidence. Effect is modest (~1 day reduction in diarrhea duration).

Zinc supplementation: WHO recommends zinc 20 mg/day x10-14 days in developing countries (reduces stool output and duration). Not routinely recommended in developed countries.

Racecadotril (enkephalinase inhibitor): Reduces intestinal hypersecretion; used in Europe and some developing countries. Not available in the US.

Complications

Hemolytic-Uremic Syndrome (HUS)

A serious complication of STEC (E. coli O157:H7) infection - a triad of:

Microangiopathic hemolytic anemia
Thrombocytopenia
Acute renal insufficiency/failure
Occurs in up to 15% of children with E. coli O157:H7 infection
Peak incidence in children <5 years (6.1 cases per 100,000/year)
Develops 7 days (up to 3 weeks) after onset of diarrhea, often as diarrhea is resolving
~50% require dialysis; 3-5% mortality
Do not give antibiotics or anti-motility agents
Early aggressive IV volume expansion reduces CNS involvement, dialysis need, and days of hospitalization

Other Complications

Electrolyte abnormalities (hyponatremia, hypernatremia, hypokalemia)
Persistent/post-infectious diarrhea (>14 days)
Bacterial translocation and sepsis
Reactive arthritis (after Salmonella, Shigella, Campylobacter, Yersinia)
Intussusception (rare, consider if pain out of proportion)

Disposition

Discharge criteria:

Well-appearing child with minimal or no dehydration
Tolerating ORT
Reliable caregiver with clear return precautions

Admission criteria:

Severe dehydration or shock
Failed ORT trial in ED
Bloody diarrhea with hemodynamic instability
Suspected HUS (falling Hb, thrombocytopenia, rising creatinine, oliguria)
Age <3 months with fever
Immunocompromised host
Unable to ensure appropriate outpatient follow-up

Prevention

Rotavirus vaccine (RotaTeq or Rotarix): Given at 2, 4 (and 6 for RV5) months. Has reduced rotavirus hospitalizations by 60-90% in immunized populations
Hand hygiene: Reduces diarrheal incidence by ~30%; alcohol-based sanitizers are effective in childcare centers
Breastfeeding: Provides passive immunity (secretory IgA) and reduces hospitalization risk
Safe food preparation, clean water access, improved sanitation

Recent Evidence (2024-2025)

Probiotics meta-analysis [PMID 40739406, J Pediatr Gastroenterol Nutr 2025]: Confirms probiotics reduce duration and severity of acute gastroenteritis in children across RCTs.
China 2024 Clinical Practice Guidelines [PMID 40437180, World J Pediatr 2025]: Updated recommendations for acute infectious diarrhea in children, emphasizing ORT, judicious antibiotic use, and zinc supplementation in resource-limited settings.

Sources:

ROSEN's Emergency Medicine, 9th Ed., Ch. 167 - "Diarrhea in Children"
Tintinalli's Emergency Medicine, Ch. 131 - "Vomiting, Diarrhea, and Dehydration in Infants and Children"
Red Book 2021, AAP Committee on Infectious Diseases
Brenner and Rector's The Kidney - Fluid Therapy for Dehydration in Children

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