Definition And Classification
- Acute Diarrhoea: Passage of >3 loose/watery stools daily, or stool volume >10 mL/kg/day in infants (>200 g/day in older children).
- Duration: Sudden onset, resolution within 7-14 days.
- Dysentery: Acute diarrhoea accompanied by visible blood and mucus, often with tenesmus and fever.
- Prolonged Diarrhoea: Episode lasting 7-13 days.
- Persistent Diarrhoea: Episode extending ≥14 days.
Epidemiology And Burden
- Accounts for ~11% of global childhood mortality; fifth leading cause of death in children <5 years.
- Global Incidence: Estimated 1.75 episodes per child <5 years annually.
- Major Risk Factors: Young age (<2 years), severe malnutrition, immunodeficiency, unsafe sanitation, lack of exclusive breastfeeding.
- Pathogen Predominance: Rotavirus remains leading cause of severe dehydrating gastroenteritis worldwide, though incidence dramatically reduced post-vaccination. Norovirus now leading cause of medical visits in highly vaccinated populations.
Etiological Profile
Enteric Infections
| Category | Specific Pathogens |
|---|---|
| Viral (50-80%) | Rotavirus, Norovirus, Sapovirus, Enteric Adenovirus (types 40/41), Astrovirus, SARS-CoV-2. |
| Bacterial | Escherichia coli (Enterotoxigenic ETEC, Enteropathogenic EPEC, Enterohemorrhagic EHEC, Enteroinvasive EIEC, Enteroaggregative EAEC). Shigella species (S. flexneri, S. sonnei, S. dysenteriae). Salmonella (nontyphoidal). Campylobacter jejuni, Yersinia enterocolitica. Vibrio cholerae (O1, O139). Clostridioides difficile. |
| Parasitic | Giardia lamblia, Cryptosporidium parvum, Entamoeba histolytica, Cyclospora, Isospora belli. |
Extra-Intestinal And Non-Infectious Causes
| Category | Associated Conditions |
|---|---|
| Systemic Infections | Otitis media, urinary tract infection, pneumonia, sepsis, meningitis. |
| Dietary/Allergic | Cow milk protein allergy, food poisoning (toxins from S. aureus, B. cereus, C. perfringens), overfeeding, hyperosmolar juices. |
| Toxic/Pharmacologic | Antibiotic-associated diarrhoea, laxative abuse, heavy metal ingestion. |
| Surgical/Anatomic | Intussusception, acute appendicitis, Hirschsprung enterocolitis, toxic megacolon, short bowel syndrome. |
Pathophysiology
Physiological Basis Of Intestinal Fluid Transport
- Normal intestine absorbs 8-9 L fluid daily; excretes 100-200 mL.
- Diarrhoea represents disturbed solute transport and water absorption.
- Rapid extracellular fluid (ECF) compartment shrinkage leads to low blood volume, hypovolemia, shock, and acute kidney injury.
- Significant loss of potassium causes hypokalemia (paralytic ileus, hypotonia).
- Loss of alkaline intestinal secretions induces severe metabolic acidosis (Kussmaul breathing).
Mechanisms Of Diarrhoea
| Mechanism | Pathogenesis | Clinical Characteristics |
|---|---|---|
| Secretory | Active ion pumping into lumen by secretagogues (e.g., cholera toxin increasing cAMP/cGMP). | Massive watery volume, persists with fasting. Normal osmolar gap (<50 mOsm/kg). |
| Osmotic | Unabsorbed luminal nutrients draw water osmotically. | Frothy/explosive stools, resolves with fasting. High osmolar gap (>100 mOsm/kg). Low stool pH (<5.5). |
| Invasive/Inflammatory | Enterocyte destruction, mucosal ulceration, cytokine release, exudation of protein/blood (Shigella, Campylobacter). | Small volume, frequent stools containing gross blood, mucus, and leukocytes (Dysentery). |
| Motility Alteration | Decreased transit time limits absorption. Delayed transit promotes bacterial overgrowth. | Variable volume, often associated with undigested food particles. |
Clinical Assessment
History
- Stool Characteristics: Frequency, volume, consistency, presence of gross blood or mucus.
- Associated Symptoms: Vomiting (onset, frequency, bilious/non-bilious), fever, abdominal cramps, tenesmus, decreased urine output.
- Epidemiological Clues: Recent travel, ill contacts, day-care attendance, unsafe water/food exposure, recent antibiotic usage.
- Dietary Intake: Pre-illness feeding practices, current fluid intake, use of inappropriate home remedies.
Physical Examination
- Vital Signs: Tachycardia, hypotension, tachypnea/hyperpnea (acidosis), fever or hypothermia.
- General Appearance: Alert, irritable, lethargic, or comatose.
- Abdominal Examination: Distension (ileus/hypokalemia), hyperactive/hypoactive bowel sounds, localized tenderness (appendicitis mimicry), palpable masses (intussusception).
- Systemic Signs: Otoscopy, respiratory evaluation to exclude extra-intestinal infections.
Dehydration Assessment (WHO/Clinical Dehydration Scale)
Accurate classification dictates the management protocol.
| Parameter | No Dehydration | Some Dehydration (Plan B) | Severe Dehydration (Plan C) |
|---|---|---|---|
| Fluid Deficit | <50 mL/kg | 50-100 mL/kg | >100 mL/kg |
| General Condition | Well, alert | Restless, irritable | Lethargic, unconscious, floppy |
| Eyes | Normal | Sunken | Deeply sunken |
| Tears | Present | Absent | Absent |
| Mouth/Tongue | Moist | Dry | Very dry |
| Thirst | Drinks normally | Thirsty, drinks eagerly | Drinks poorly or unable to drink |
| Skin Pinch | Goes back quickly | Goes back slowly (<2 sec) | Goes back very slowly (>2 sec) |
| Pulse/Breathing | Normal | Tachycardia, normal/fast breathing | Weak/thready pulse, deep/rapid breathing |
Diagnostic Evaluation
Indications For Laboratory Testing
Routine investigations are unnecessary for self-limiting watery diarrhoea. Testing is indicated for:
- Age <3 months.
- Toxic or septic appearance, shock.
- Dysentery (gross blood/mucus).
- Prolonged diarrhoea (>14 days).
- Immunocompromised state.
- Suspected outbreaks or recent foreign travel.
Specific Investigations
| Investigation | Utility And Findings |
|---|---|
| Stool Microscopy | Darting motility (V. cholerae); Trophozoites/cysts (Giardia, E. histolytica); Fecal leukocytes/RBCs (invasive bacterial enteritis). |
| Multiplex PCR/NAAT | Rapid, high-sensitivity detection of viral, bacterial, and parasitic genomes. Replaced routine culture in many settings. |
| Stool Culture | Indicated for suspected Shigella, Salmonella, Campylobacter, Yersinia, Vibrio. Essential for antimicrobial susceptibility testing. |
| Clostridioides difficile Testing | Toxin A/B EIA, Glutamate dehydrogenase (GDH) antigen, or NAAT. Not recommended <2 years due to high asymptomatic carriage. |
| Serum Biochemistry | BUN, Creatinine, Electrolytes (Na, K, Cl), Venous Blood Gas. Indicated for severe dehydration, altered sensorium, ileus, or suspected Hemolytic Uremic Syndrome (HUS). |
| Complete Blood Count | Leukocytosis with bandemia (sepsis, Shigella), Anemia/Thrombocytopenia (suspect HUS secondary to STEC/Shigella). |
Management Protocol
Core Principles
- Rehydration and maintenance of hydration.
- Continued enteral feeding.
- Zinc supplementation.
- Selective, judicious use of antimicrobials.
1. Rehydration Therapy
Utilizes Oral Rehydration Solution (ORS). WHO low-osmolarity ORS (Sodium 75 mEq/L, Glucose 75 mmol/L, total osmolarity 245 mOsm/L) exploits the intact sodium-glucose intestinal cotransporter, significantly reducing stool output and IV fluid requirement.
Plan A: No Dehydration (Home Management)
- Goal: Prevent dehydration by replacing ongoing losses.
- Fluid administration: Give WHO ORS after each loose stool.
- Age <24 months: 50-100 mL per stool (up to 500 mL/day).
- Age 2-10 years: 100-200 mL per stool (up to 1000 mL/day).
- Age >10 years: Ad libitum.
- Instructions: Continue regular feeding/breastfeeding. Monitor for danger signs (intractable vomiting, bloody stool, absent urine, altered sensorium).
Plan B: Some Dehydration (Facility Management)
- Goal: Correct deficit over 4 hours using ORS.
- Dose: 75 mL/kg ORS administered over 4 hours.
- Administration: Frequent small sips via spoon/cup. If vomiting occurs, wait 10 minutes, then resume at a slower rate. Nasogastric tube if oral intake refused.
- Maintenance: Add 10 mL/kg ORS for every ongoing loose stool.
- Reassess hydration status after 4 hours. Transition to Plan A if resolved, or Plan C if deteriorating.
Plan C: Severe Dehydration (Hospital Emergency)
- Goal: Immediate intravascular volume expansion to prevent ischemic organ damage.
- Fluid Choice: Isotonic crystalloid (Ringer’s Lactate with 5% Dextrose, or 0.9% Normal Saline).
- Resuscitation Volumes (100 mL/kg total):
- Infants <12 months: 30 mL/kg IV over 1 hour, followed by 70 mL/kg over 5 hours.
- Children >12 months: 30 mL/kg IV over 30 minutes, followed by 70 mL/kg over 2.5 hours.
- Note: Severe malnutrition with shock requires slower resuscitation (15 mL/kg over 1 hour) due to heart failure risk. Use half-normal saline with 5% dextrose.
- Reassess pulses and sensorium every 15-30 minutes. Initiate ORS via nasogastric tube (20 mL/kg/hr) simultaneously if IV access impossible.
2. Nutritional Rehabilitation
- Early Refeeding: Do not restrict diet. Bowel rest aggravates villous atrophy and prolongs diarrhoea.
- Breastfeeding: Continue uninterrupted throughout rehydration and maintenance phases.
- Diet Composition: Resume age-appropriate complex carbohydrates, lean meats, yoghurt, and vegetables. Energy density should target ~1 kcal/g.
- Avoid: High-osmolar fruit juices, carbonated beverages, foods high in simple sugars or fats.
- Lactose-Free Diet: Routine use not recommended. Reserved for persistent diarrhoea or explosive, acidic stools with severe perianal excoriation indicating secondary lactase deficiency.
3. Adjunctive Therapies
Zinc Supplementation
- Indication: Universal administration in developing nations.
- Mechanism: Promotes enterocyte regeneration, restores brush border enzymes, enhances local immunity.
- Dose: 20 mg/day elemental zinc for 10-14 days (10 mg/day for infants <6 months).
- Outcome: Significantly reduces severity, duration, and risk of persistent diarrhoea/reinfection over next 3 months.
Probiotics
- Efficacy: Strain-dependent. Documented to reduce diarrhoeal duration by ~1 day, primarily in viral (Rotavirus) gastroenteritis.
- Recommended Strains: Lactobacillus rhamnosus GG (LGG) (≥10^10 CFU/day) and Saccharomyces boulardii (250-750 mg/day) for 5-7 days.
- Contraindications: Severely immunocompromised, indwelling central venous catheters (risk of fungemia/bacteremia).
4. Symptomatic Pharmacotherapy
- Antiemetics: Single-dose oral or IV Ondansetron (0.15 mg/kg) may be given if intractable vomiting prevents successful ORS administration.
- Antisecretory Agents: Racecadotril (enkephalinase inhibitor) reduces stool output and duration without affecting motility. Efficacy evidence is moderate.
- Antimotility Agents: Loperamide, diphenoxylate. Strictly contraindicated in children. Risk of paralytic ileus, bacterial overgrowth, toxic megacolon, and severe CNS depression.
5. Antimicrobial Therapy
Empiric antibiotics are generally not indicated for acute watery diarrhoea (mostly viral). Indiscriminate use promotes resistance, disrupts microbiome, and prolongs carrier states (e.g., Salmonella).
Specific Indications for Antibiotics:
- Dysentery (Bloody Diarrhoea): Presumed Shigella. Intravenous Ceftriaxone (50-100 mg/kg/day for 3-5 days), oral Azithromycin (12 mg/kg day 1, 6 mg/kg days 2-3), or Ciprofloxacin.
- Cholera: Severe dehydration with suspected cholera. Azithromycin (single dose) or Doxycycline.
- Campylobacteriosis: Severe dysenteric presentation. Azithromycin.
- C. difficile Colitis: Discontinue offending antibiotic. Oral Metronidazole (30 mg/kg/day) or Oral Vancomycin (40 mg/kg/day) for 10-14 days.
- Parasitic Infections: Giardia lamblia or Entamoeba histolytica with persistent symptoms. Tinidazole, Nitazoxanide, or Metronidazole.
- High-Risk Hosts: Infants <3 months, immunocompromised, severe acute malnutrition, associated systemic sepsis.
Complications
- Metabolic/Renal: Severe dehydration, hypovolemic shock, hypokalemic nephropathy, acute tubular necrosis, metabolic acidosis.
- Neurological: Febrile seizures, encephalopathy, cerebral venous sinus thrombosis (due to severe dehydration/hypernatremia).
- Gastrointestinal: Toxic megacolon, intestinal perforation, rectal prolapse, transient protein-losing enteropathy, post-infectious irritable bowel syndrome.
- Systemic: Hemolytic Uremic Syndrome (HUS) secondary to Shiga-toxin producing E. coli or Shigella dysenteriae (microangiopathic hemolytic anemia, thrombocytopenia, acute kidney injury).
- Nutritional: Weight loss, secondary lactase deficiency, transition to persistent diarrhoea, severe acute malnutrition.
Prevention Strategies
- Immunization: Universal Rotavirus vaccination dramatically reduces severe diarrhoeal hospitalizations and mortality. Oral cholera vaccines utilized in endemic settings/outbreaks.
- Nutrition: Promotion of exclusive breastfeeding for the first 6 months of life provides maternal IgA antibodies and lowers exposure to contaminated formulas.
- WASH Interventions: Water, Sanitation, and Hygiene. Access to safe drinking water, improved sewage disposal, and rigorous handwashing practices drastically reduce transmission of enteric pathogens.