This lecture, delivered by Dr. Pamela Lee (Department of Paediatrics & Adolescent Medicine), is a clinically-oriented walkthrough of how to approach a child presenting with diarrhoea — from history-taking and clinical assessment of dehydration, through to fluid management, nutritional advice, pharmacological (non-)interventions, antibiotic indications, and discharge planning. It also contextualizes paediatric gastroenteritis (GE) within the global child-mortality landscape. ^[1]

1. Define diarrhoea in children and differentiate acute from chronic causes
2. Identify the commonest aetiologies of acute infective GE (viral, bacterial, protozoal)
3. Perform a systematic history and clinical assessment, including dehydration severity
4. Recognize red-flag features suggesting diagnoses other than GE or progression to shock
5. Know when to investigate (bloods, stool microbiology) — and when NOT to
6. Master fluid management: oral rehydration therapy (ORT) vs IV fluids, including shock management
7. Understand nutritional management principles (no diluted milk, no special formula)
8. Know which pharmacological agents to avoid in children (anti-emetics, anti-diarrhoeals)
9. Identify the specific indications for antibiotics in paediatric GE
10. Counsel parents and carers on home management, red-flag signs, and expected disease course
11. Appreciate the global perspective: diarrhoeal disease and under-5 mortality

• Exams: Frequently tested in MCQ, SAQ, and minicase formats. Past papers (e.g., 2022 Q87) directly examine fluid management decisions ^[7]. Intussusception (a differential for bloody stool in children) is another favourite (2023 minicase Case 2) ^[8].
• Clinical practice: Acute GE is one of the commonest reasons for paediatric ED visits and hospitalization. Getting dehydration assessment and ORS right saves lives.

Normal stool pattern varies between children — a breastfed neonate may pass 6–8 soft stools per day. The definition requires a change from baseline, not an arbitrary number.

Differential diagnosis of acute-onset bloody stool, fever, and abdominal cramps includes: Campylobacter, Shigella, Salmonella, Clostridium difficile, Yersinia enterocolitica, Vibrio parahaemolyticus, Enteroinvasive E. coli, Enterohemorrhagic E. coli (O157:H7), and initial presentation of inflammatory bowel disease. ^[1]

Why this matters from first principles: Watery stool occurs when the toxin stimulates secretion (secretory mechanism) or the virus destroys absorptive villous cells (e.g., rotavirus) → net water loss into the lumen. Bloody/mucoid stool occurs when the organism invades or directly damages the colonic mucosa, exposing blood vessels and provoking an inflammatory exudate (mucus + PMNs).

Is this truly "diarrhoea"? Characterize: watery vs bloody, presence of mucus. Acute or chronic? ^[1]

Why: Parents may call any loose stool "diarrhoea." You must establish the baseline stool pattern and the nature of the change. The character (watery vs bloody/mucoid) immediately stratifies the likely mechanism and pathogen group.

Number of episodes, frequency, estimated amount as judged by the parents. ^[1]

Why: This quantifies the magnitude of fluid loss. A child passing 10 large watery stools in 6 hours is at far higher risk of dehydration than one with 3 small loose stools over 24 hours.

Vomiting, fever, poor appetite (quantify intake), abdominal pain, irritability. ^[1]

Why:

• Vomiting → additional fluid loss + compromises oral rehydration
• Fever → increases insensible losses + suggests infective cause
• Poor appetite → child not replacing losses
• Irritability → may be an early sign of dehydration or intracranial pathology

Symptoms: dry lips, cool limbs, decreased urine output. ^[1] Risk factors: frequent profuse watery diarrhoea, vomiting, poor fluid intake, concurrent fever. ^[1]

Why: This step directly determines whether the child needs clinic/home management vs. hospital-based rehydration. Each risk factor increases obligatory fluid losses or decreases intake.

Acute diarrhoea DDx: Infective (bacterial vs viral, secretory vs inflammatory), food intolerance, osmotic agents, drugs. Also consider chronic diarrhoea. ^[1]

Why: Not every child with loose stools has GE. Consider osmotic diarrhoea from fruit juices (sorbitol), drug-related (antibiotics), food intolerance (cow's milk protein allergy in infants), or the onset of chronic conditions.

Usual intake, change in content/preparation/utensils, undercooked or raw food, eating out, contact with persons with similar symptoms, nursery attendance, occupation of family members (cooks, kitchen workers, healthcare workers). ^[1]

Why: Identifying the source is crucial for infection control and public health reporting. If the child attends daycare, an outbreak investigation may be triggered.

Setting (child-care centres, institutions, hospitals), family/close contacts, food-borne or water-borne after common exposure, antimicrobial-associated diarrhoea, traveller's diarrhoea, immunocompromised host, history of chronic diarrhoea or underlying GI disease. ^[1]

Did the mother give sufficient fluid? How well tolerated? Any medications given? Already seen a doctor? ^[1]

Why: This avoids duplication, identifies failed interventions (e.g., child vomited all ORS → may need IV), and reveals potentially harmful treatments (e.g., loperamide given by family).

Recurrent diarrhoea, growth pattern, diet, birth history, immunization, family history, social history. ^[1]

Why: Recurrent diarrhoea may suggest immunodeficiency, IBD, coeliac disease, or cow's milk protein allergy. Growth faltering in a child with chronic loose stools is a red flag for malabsorption. Immunization history (rotavirus vaccine) is relevant for risk stratification.

Most common: Salmonella. Others: Campylobacter, E. coli, Cryptosporidium. Shigella, Giardia, Entamoeba (Indian subcontinent, sub-Saharan and southern Africa). ^[1]

Rotavirus infects and destroys the mature enterocytes at the tips of the intestinal villi. These cells are responsible for absorption; the immature crypt cells that replace them are net secretors. The result is osmotic diarrhoea (malabsorption of carbohydrates) + secretory diarrhoea (immature crypt cells). This dual mechanism explains the profuse watery stool. In developed countries, rotavirus accounts for 25–55% of all hospitalizations for GE ^[1].

Characteristics that may suggest a diagnosis other than GE ^[1]

Key differentials to consider when a child presents with diarrhoea and/or vomiting but doesn't fit the GE pattern:

This is a three-tier classification: No clinical dehydration → Clinical dehydration → Clinical shock. ^[1]

Within the category of 'clinical dehydration' there is a spectrum of severity indicated by increasingly numerous and more pronounced symptoms and signs. Symptoms and signs with red flags may help identify children at increased risk of progression to shock. ^[1]

Dehydration with plasma Na > 150 mmol/L. ^[1]

'Doughy skin' is not reliable to identify patients with hypernatraemic dehydration. Severity of dehydration is more often underestimated compared with normo-natraemic dehydration. ^[1]

Why dehydration is underestimated: In hypernatraemia, water shifts from the intracellular to the extracellular compartment (osmosis). This relatively preserves the intravascular volume, so signs of dehydration (skin turgor, capillary refill) appear less severe than the actual total body water deficit.

Suspect hypernatraemic dehydration if there are: jittery movements, increased muscle tone, hyper-reflexia, convulsions, drowsiness or coma. ^[1]

Why neurological signs: The brain cells shrink as water moves out due to the hyperosmolar extracellular fluid. This can tear bridging veins (cerebral haemorrhage) and cause direct neuronal damage. Additionally, during correction, if Na is lowered too rapidly, water rushes back into brain cells → cerebral oedema → seizures.

Do not routinely perform blood biochemical testing. ^[1]

Measure plasma Na, K, urea, creatinine & glucose if: IV fluid therapy is required, symptoms/signs suggest hypernatraemia, unexplained drowsiness in an infant (rule out hypoglycaemia). ^[1]

Measure venous blood acid-base status and chloride concentration if shock is suspected or confirmed. ^[1]

Causes: loss of bicarbonate in diarrhoea (normal anion gap metabolic acidosis), lactic acidosis in hypovolaemic shock (raised anion gap metabolic acidosis). ^[1]

Why this distinction matters: Normal anion gap acidosis from diarrhoea is expected and corrects with rehydration. A raised anion gap suggests tissue hypoperfusion (shock) and is a much more ominous sign requiring aggressive fluid resuscitation.

Most acute GE in children are viral in origin. Even if bacterial, most do not require antimicrobial treatment. Identification of a specific pathogen is not generally required. ^[1]

Continue breastfeeding and other milk feeds. Encourage fluid intake. Discourage fruit juices and carbonated drinks. Offer ORS as supplemental fluid to those at increased risk of dehydration. ^[1]

Why avoid fruit juice: Fruit juices contain high concentrations of fructose and sorbitol, which are poorly absorbed → osmotic diarrhoea, worsening the problem. Carbonated drinks are hyperosmolar and lack electrolytes.

ORS is the first choice for rehydration. Use ORS for replacing fluid deficit in the first 3–4 hours of the rehydration phase. Continue breastfeeding and milk feeds. ^[1]

Oral rehydration strategy: small, frequent feeds. Replace fluid deficit over 4 hours. Ensure appropriate maintenance fluid. Monitor ongoing loss and replace accordingly. Reassess! Reassess! Reassess! ^[1]

Why small frequent feeds: Large boluses trigger vomiting via gastric distension → defeats the purpose. The stomach can handle small volumes (5–10 mL every 1–2 minutes) even in a vomiting child.

Low-osmolarity ORS ( < 250 mOsm/L) reduces the need for unscheduled IV fluid, and leads to greater reduction in stool output and vomiting compared with high-osmolarity ORS. ^[1]

Why low-osmolarity is better: High-osmolarity ORS in the gut lumen draws water into the lumen by osmosis → can paradoxically worsen diarrhoea. Low-osmolarity ORS allows net water absorption.

At the brush border, rice starch is broken down into glucose by polysaccharidase and disaccharidase. Na-glucose co-transporter promotes absorption of salts and water into the lumen of intestinal villi. ^[1]

Why rice-based works well: Rice starch provides glucose molecules slowly (as they are enzymatically released from the polymer) rather than as a sudden osmotic load. This maximizes Na-glucose co-transport (SGLT1) without increasing luminal osmolarity. Evidence shows particular benefit in cholera ^[1].

Use IV fluid if: signs of shock, impaired conscious state, clinical deterioration despite ORT, failure of ORT (e.g., intolerance due to persistent vomiting), paralytic ileus. ^[1]

Rapid IV 0.9% NaCl, 20 mL/kg → If shock persists, repeat 20 mL/kg and consider other causes of shock → If shock still persists, consult intensive care. ^[1]

Why 0.9% NaCl: It is an isotonic crystalloid that stays in the intravascular space better than hypotonic solutions. In shock, the priority is restoring circulating volume rapidly.

WHO recommends IV rehydration to correct fluid deficit in 3–6 hours. Attempt early and gradual introduction of ORT during IV therapy. If tolerated, stop IV and complete rehydration with ORT. ^[1]

Use isotonic solution (0.9% NaCl) for deficit replacement and maintenance. Replace fluid deficit slowly — over 48 hours. Monitor plasma Na frequently, aiming to reduce it at < 0.5 mmol/L per hour. ^[1]

Why so slow: Rapid reduction in serum Na → osmotic gradient reverses → water rushes into brain cells → cerebral oedema → seizures, permanent brain injury, or death. The 48-hour timeline and < 0.5 mmol/L/hour rate are critical safety guardrails.

Encourage breastfeeding and milk feeds. Replace ongoing loss with ORS 5–10 mL/kg per large watery stool for at-risk groups: children < 1 year (especially < 6 months), low birth weight infants, > 5 diarrhoeal stools in previous 24 hours, > 2 vomits in previous 24 hours. ^[1]

Most children have self-limiting vomiting; routine use of ondansetron not recommended. Use of promethazine and metoclopramide has significant adverse effects (dystonic reactions, oculogyric crisis) — do not use in children. ^[1]

Why ondansetron increases stool: By stopping vomiting, fluid and toxins that would have been expelled upward are retained and pass through the gut → more diarrhoea. This is an important trade-off to understand.

Adsorbents (kaolin, smectite), anti-motility agents (loperamide) — no high-level evidence of benefit, NOT recommended. Potentially serious adverse effects: abdominal distension, ileus, drowsiness (loperamide); increased intestinal transit time reduces clearance of pathogens and toxins. ^[1]

"A live microbial food ingredient that, when ingested in sufficient quantities, exerts health benefits on the consumer." ^[1]

Mechanisms:

• Compete with pathogens for binding sites and substrates
• Lower intestinal luminal pH
• Upregulate genes mediating immunity
• Produce trophic short-chain fatty acids promoting mucosal cell growth and differentiation ^[1]

Examples: Lactobacillus, Bifidobacillus, Saccharomyces yeast. Some evidence for Lactobacillus casei GG as a useful adjunct. Dosage: ≥10 billion CFU/day for 5–7 days ^[1][2].

Rehydration completed, minimal risk for recurrence of dehydration, uncomplicated disease course. Also consider: reliable carer, understanding of the treatment plan, myths and misunderstandings. ^[1]

Most children with GE can be safely managed at home. Empower parents and carers. ^[1]

Home management advice:

• Continue usual feeds including breastfeeding
• Encourage plenty of fluids, small frequent portions
• Avoid fruit juices and carbonated drinks
• Offer ORS as supplemental fluid

Red-flag symptoms to seek medical attention:

• Appears more unwell, altered responsiveness, irritability, lethargy
• Decreased urine output
• Pale, mottled skin; cold extremities ^[1]

Expected course:

• Diarrhoea: 5–7 days, most stops within 2 weeks
• Vomiting: 1–2 days, most stops within 3 days ^[1]

If symptoms exceed these timelines → return for reassessment.

Commonly tested alongside GE because it presents with vomiting and bloody stool ("redcurrant jelly") in a similar age group. ^[8]

Always think of this when EHEC O157:H7 is the cause of bloody diarrhoea. Triad: microangiopathic haemolytic anaemia + thrombocytopaenia + acute kidney injury. Antibiotics may worsen it. ^[1][4]

Stem: 19-month-old boy with vomiting and diarrhoea for 3 days. Tired but responsive, warm peripheries, CRT 3 sec, HR 120, large watery stool, vomited twice in A&E. Options: (A) IV maintenance, (B) Oral rehydration alone, (C) OG tube, (D) Replace deficit and ongoing loss by IV ^[7].

Likely answer: This child has clinical dehydration (CRT 3 sec, tired) but is responsive with warm peripheries → NOT in shock. However, he is vomiting (vomited twice in ED), which threatens ORS tolerance. The correct answer depends on whether you think oral rehydration can still be attempted:

• The lecture says ORS is the first choice and IV is reserved for shock, impaired consciousness, deterioration despite ORS, or persistent vomiting. Vomiting twice doesn't yet meet "failure of oral rehydration."
• However, the question asks for "MOST APPROPRIATE" — with ongoing vomiting and 3 days of worsening, answer (D) (replace deficit and ongoing loss by IV) is likely the intended answer, as the clinical picture suggests oral tolerance is failing.

1. "Which pathogen is the commonest cause of GE in children?" → Rotavirus
2. "When do you give antibiotics in paediatric GE?" → The 9-point list above
3. "What ORS should you use?" → Low-osmolarity (WHO post-2002)
4. "Should you give loperamide/metoclopramide to a child?" → No
5. "How do you correct hypernatraemic dehydration?" → Slowly, over 48 hours, isotonic fluid, < 0.5 mmol/L/hour
6. "What is the anion gap in diarrhoeal acidosis?" → Normal (bicarbonate loss)
7. "Should you dilute milk?" → No evidence of benefit; give full-strength