Preparatory Mindset
Paediatric GI in this syllabus covers acute diarrhoea (gastroenteritis — the dehydration calculation) and peptic ulcer disease — with the mindset centred on fluid and electrolyte management. The exam focus:
- Acute gastroenteritis: viral (rotavirus — most common cause of severe childhood diarrhoea; norovirus) vs bacterial (Shigella, Salmonella, E. coli, Campylobacter) — the danger is dehydration, not the pathogen → assess dehydration (WHO: none/some/severe), rehydrate (ORS, IV for severe), zinc + early feeding, NO routine antibiotics, NO antiemetics/antidiarrhoeals. Rotavirus vaccine prevents the worst.
- Peptic ulcer disease (children): H. pylori (most common cause), NSAIDs, stress — epigastric pain, haematemesis/melaena; diagnosis — endoscopy (gold) + urea breath test/stool antigen; treatment — PPI + amoxicillin + clarithromycin (± metronidazole) triple therapy × 14 days.
- Recurrent abdominal pain (RAP): functional in most — but red flags (weight loss, night pain, fever, blood, family history) → organic workup.
The OSCE pattern: "calculate this child's dehydration and prescribe ORS/IV fluids" and "counsel on gastroenteritis management".
Core Concepts
1. Acute gastroenteritis (AGE)
Aetiology:
| Pathogen | Features |
|---|---|
| Rotavirus | Most common cause of severe dehydrating gastroenteritis in young children; winter; watery diarrhoea + vomiting + fever; vaccine-preventable |
| Norovirus | Outbreaks (schools, cruises); projectile vomiting |
| Adenovirus/astrovirus | Milder |
| Bacterial — Shigella, Salmonella, Campylobacter, E. coli (ETEC/EHEC) | Bloody stools, high fever, toxic; food poisoning links |
| Parasites | Giardia (prolonged), Cryptosporidium |
Clinical: vomiting (first, often resolves 24-48 h), watery diarrhoea, fever, abdominal pain; complications — dehydration (the big one), electrolyte imbalance, hypoglycaemia (young), seizures (febrile or salt/water imbalance), HUS (EHEC — bloody diarrhoea + pallor + oliguria + ↓platelets), malnutrition.
Dehydration assessment (WHO):
| Grade | % loss | Signs |
|---|---|---|
| No/some (mild) | <5% | Thirsty, alert, normal eyes/tears, skin pinch returns slowly |
| Moderate (some) | 5-10% | Restless/irritable, sunken eyes, ↓ tears, ↓ skin turgor (slow pinch), dry mouth |
| Severe | >10% | Lethargic/unconscious, very sunken eyes, very slow skin turgor, unable to drink, weak pulse, cold extremities, oliguria → SHOCK — IV fluids urgently |
Investigations: usually clinical (no routine stool culture/bloods); stool culture if: blood/mucus, age <3 months, immunocompromised, recent antibiotics/travel, outbreak; electrolytes/glucose if severe dehydration, IV fluids needed, or young infant.
Management:
| Plan | Details |
|---|---|
| Rehydration (mild-moderate) | Low-osmolarity ORS — 75 mL/kg over 4 h (small frequent amounts), then replace ongoing losses (10 mL/kg per loose stool); breastfed infants continue breastfeeding |
| Severe dehydration | IV Ringer's lactate/0.9% saline 20 mL/kg bolus (repeat until perfused) → then IV maintenance + replacement; switch to ORS when drinking |
| Early feeding | Resume normal diet/breastfeeding as soon as possible — no starvation (reduces duration) |
| Zinc | 10-20 mg/day × 10-14 days (children <5) — reduces severity and duration |
| Antibiotics | NOT routine (viral); Shigella dysentery / cholera / immunocompromised / sepsis → targeted antibiotics |
| Antiemetics/antidiarrhoeals | Avoid (loperamide contraindicated in children — paralytic ileus risk); ondansetron sometimes for severe vomiting (specialist) |
| Prevention | Rotavirus vaccine (oral, 2/3 doses by 6 months); hand hygiene; safe water; food hygiene |
2. Peptic ulcer disease (PUD) in children
Definition: gastric/duodenal ulcer — duodenal more common in children (and H. pylori-associated).
Causes:
- H. pylori infection (most common — chronic gastritis → duodenal ulcer)
- NSAIDs (aspirin, ibuprofen)
- Stress ulcers (severe illness, burns — Curling, head injury — Cushing)
- Zollinger-Ellison (gastrinoma — rare)
- Corticosteroids (controversial)
Clinical: epigastric pain (burning), pain before meals/at night (duodenal) or after meals (gastric), nausea, bloating, haematemesis/melaena, iron-deficiency anaemia (chronic occult bleeding); infants/young children — feeding difficulty, failure to thrive, vomiting.
Diagnosis:
- Endoscopy (OGD) — gold standard (visualise ulcer, biopsy for H. pylori — rapid urease test, histology, culture).
- Non-invasive H. pylori tests — urea breath test (UBT), stool antigen (not blood serology — stays positive after cure).
- Barium meal (older; less used).
Management:
- PPI (omeprazole) — acid suppression, symptom relief, ulcer healing.
- H. pylori eradication — triple therapy × 14 days: PPI + amoxicillin + clarithromycin (or metronidazole instead of amoxicillin if penicillin-allergic); quadruple therapy (PPI + bismuth + metronidazole + tetracycline) for resistance.
- Stop NSAIDs (switch to paracetamol); H2-blockers alternative.
- Complications: bleeding (endoscopic haemostasis, IV PPI), perforation (surgery), gastric outlet obstruction.
- Follow-up — confirm H. pylori eradication (UBT at least 4 weeks after treatment, off PPI 2 weeks).
3. Recurrent abdominal pain (RAP)
Definition: ≥3 episodes of abdominal pain over ≥3 months, affecting activity. Most (90%) is functional (functional abdominal pain, IBS, functional dyspepsia) — but organic causes must be excluded.
Red flags (organic): weight loss/faltering growth, night-time waking pain, fever, vomiting, blood in stool, jaundice, joint pain, rash, family history of IBD/coeliac, localised/right iliac fossa tenderness, abnormal examination.
Organic causes to consider: coeliac disease, IBD, GORD, constipation (very common), UTI, mesenteric adenitis, H. pylori, intussusception (infants), surgical (appendicitis — right iliac fossa + fever + anorexia).
Management: history + exam + red flag screen (FBC, coeliac serology, urinalysis, ± stool calprotectin, USS); if negative → reassure + functional management (diet, fibre, gut-directed hypnotherapy, treat constipation); avoid repeated investigations for functional pain.
High-Yield Points
| Topic | Must-remember |
|---|---|
| Rotavirus | Most common severe childhood gastroenteritis; vaccine |
| Dehydration severe | >10% — lethargy, very sunken eyes, very ↓ turgor, unable to drink, shock |
| ORS | 75 mL/kg over 4 h (mild-moderate) + replace losses |
| Severe dehydration | IV 20 mL/kg bolus |
| Early feeding | Resume diet asap — no starvation |
| Zinc | 10-20 mg/day × 10-14 d (children <5) |
| Antidiarrhoeals | Avoid loperamide in children |
| Rotavirus vaccine | Oral, by 6 months |
| PUD cause | H. pylori most common; NSAIDs |
| H. pylori tests | UBT/stool antigen (not serology); endoscopy = gold |
| Eradication | PPI + amoxicillin + clarithromycin × 14 days |
| Eradication check | UBT 4 weeks after, off PPI 2 weeks |
| RAP | Most functional — red flags → organic workup |
| RAP red flags | Weight loss, night pain, fever, blood, family history |
Topic Summary
Acute gastroenteritis (rotavirus most common) is managed by dehydration assessment → ORS (75 mL/kg over 4 h) or IV fluids (severe — 20 mL/kg bolus) → early feeding + zinc (10-20 mg × 10-14 d) → no routine antibiotics/antiemetics/antidiarrhoeals; rotavirus vaccine prevents the worst. Peptic ulcer disease — H. pylori (most common) + NSAIDs; diagnose with endoscopy (gold) or UBT/stool antigen; treat with PPI triple therapy × 14 days + stop NSAIDs; confirm eradication. Recurrent abdominal pain is mostly functional but always screen for red flags (weight loss, night pain, fever, blood, family history).
LMCHK OSCE Practice — The Dehydrated Toddler
Station setup: A 15-month-old toddler presents with 2 days of watery diarrhoea (8-10 stools/day) and vomiting (now settled). He is restless and thirsty, with sunken eyes, dry mouth, and skin pinch returning slowly (2-3 s). Weight 10 kg. No blood in stool, no fever.
Candidate tasks (8 min):
- Assess dehydration severity — some (moderate, 5-10%) dehydration (restless, sunken eyes, ↓ turgor, thirsty, no shock).
- Prescribe ORS: 75 mL/kg = 750 mL over 4 h in small frequent sips; continue breastfeeding; replace ongoing losses (10 mL/kg per stool).
- Explain zinc (10-20 mg/day × 14 days) and early feeding (resume normal diet/breastfeeding).
- State what to avoid: no antibiotics (viral), no antidiarrhoeals (loperamide contraindicated).
- Give red flags to return: lethargy, no urine, blood in stool, high fever, inability to drink, vomiting of everything → IV rehydration.
Key marking cues:
- Correct dehydration grade and ORS volume calculation (75 mL/kg over 4 h).
- Zinc + early feeding — the modern WHO recommendations.
- No antibiotics/antidiarrhoeals for viral AGE.
- Clear return advice (worsening dehydration, blood, high fever).
- Handles the calculation confidently — the exam point.