Chapter 19 · Alimentary Tract & Liver (Mouth – Small Intestine)

GI function (digestion, transport, motility, immunity, endocrine) · Oral pathology · Esophagus (GORD, EoE, achalasia) · Stomach (gastritis, peptic ulcer, H. pylori, upper GI bleeding, vomiting, IHPS) · Small intestine (structure, digestion, absorption, motility, immunity)
📌 Core principles: Gastroesophageal reflux is common in infants; pathological GORD causes faltering growth/oesophagitis. H. pylori infection requires test-and-treat in symptomatic children. Infantile hypertrophic pyloric stenosis presents with projectile non-bilious vomiting at 2–8 weeks. Small intestine is main site for nutrient digestion/absorption; immune defences involve Peyer’s patches and IgA.

📖 Alimentary tract: key concepts

🔬 GI function
Digestion (enzymes, bile), transport (peristalsis), motility (migrating motor complex), immunity (GALT, IgA), endocrine (gut hormones: gastrin, secretin, CCK).
👄 Mouth
Lips (cheilitis, angular stomatitis), mucosa (aphthous, candidiasis, Koplik spots), gums (hyperplasia, bleeding), tongue (geographic, macroglossia, strawberry tongue), teeth (enamel defects, delayed eruption), salivary glands (parotitis, sialolithiasis).
🌿 Esophagus
Structure (squamous epithelium, lower sphincter), dysphagia (oropharyngeal vs esophageal), GORD (physiological vs pathological: PPI, fundoplication), eosinophilic esophagitis (topical steroids, elimination diet), achalasia (Heller myotomy).
🧪 Stomach & duodenum
Gastritis (NSAIDs, H. pylori), peptic ulcer (duodenal more common), H. pylori test (stool antigen, urea breath test, biopsy), upper GI bleeding (varices, ulcer, erosions), vomiting (bilious vs non-bilious), infantile hypertrophic pyloric stenosis (olive sign, hypochloremic metabolic alkalosis), cyclical vomiting syndrome (migraine variant).
🍽️ Small intestine
Structure (villi, crypts, microvilli), digestion (brush border disaccharidases, peptidases), absorption (glucose, amino acids, lipids, B12, iron), motility (migrating motor complex), immune defences (Peyer’s patches, intraepithelial lymphocytes, secretory IgA).

🔎 Symptom-based approach: vomiting, dysphagia, abdominal pain

1️⃣
Projectile non-bilious vomiting in a 4-week-old – Infantile hypertrophic pyloric stenosis (IHPS). Hypochloremic metabolic alkalosis, palpable olive, ultrasound confirms pyloric stenosis.
2️⃣
Chronic intermittent vomiting + epigastric burning + family history of H. pylori – Test for H. pylori (stool antigen or urea breath test). Treat with triple therapy (PPI + amoxicillin + clarithromycin).
3️⃣
Dysphagia to solids (food impaction) + atopy + linear furrows on endoscopy – Eosinophilic esophagitis (EoE). Biopsy shows ≥15 eosinophils/HPF. Treat with PPI trial, swallowed topical steroids.
4️⃣
Infant with regurgitation, irritability, and poor weight gain despite antireflux measures – Pathological GORD. Oesophageal pH/impedance monitoring, upper endoscopy for oesophagitis. PPI therapy (omeprazole).
5️⃣
Paroxysmal episodes of intense vomiting separated by well intervals, normal growth, associated with pallor and migraine – Cyclical vomiting syndrome. Treat prophylactically (amitriptyline, cyproheptadine, mitochondrial cocktail).
⚠️ Red flags in vomiting: Bilious vomiting (obstruction until proven otherwise), haematemesis (varices, ulcer), neurological signs (raised ICP), bulging fontanelle, hepatosplenomegaly (metabolic).

📋 Management algorithms: GORD, IHPS, H. pylori, Upper GI bleeding

🩺
Infantile hypertrophic pyloric stenosis (IHPS) – management
▪️ Correct dehydration and metabolic alkalosis (IV 0.9% saline + KCl).
▪️ Pyloromyotomy (Ramstedt) – laparoscopic or open.
▪️ Post-op: resume feeds within 4–6h, monitor for adequate intake.
💊
H. pylori infection – treatment (positive test in symptomatic child)
▪️ First-line: PPI (omeprazole) + amoxicillin + clarithromycin for 14 days (triple therapy).
▪️ Second-line: bismuth quadruple therapy or levofloxacin-based.
▪️ Test-of-cure (stool antigen) 4 weeks after completion.
🌿
Gastroesophageal reflux disease (GORD) – step-up approach
▪️ Lifestyle: thickened feeds, avoid overfeeding, upright after feeds.
▪️ Pharmacological: PPI (omeprazole 1–2 mg/kg/day) for 4–8 weeks; prokinetics not recommended.
▪️ Surgical fundoplication (Nissen) if refractory or life-threatening aspiration.
🍽️
Upper GI bleeding (non-variceal) – management
▪️ Resuscitation: IV access, cross-match, PPI infusion (pantoprazole).
▪️ Endoscopy within 24h for high-risk stigmata (active bleeding, visible vessel).
▪️ Haemoclip or adrenaline injection + thermal coagulation if needed.

💡 Reflex prompts – Esophagus, stomach, small intestine

🍼 A 5-week-old with projectile vomiting, weight loss, and visible peristalsis. Electrolyte abnormality?
Hypochloremic metabolic alkalosis (loss of gastric acid). Classic for IHPS.
🩸 A child with recurrent epigastric pain, melena, and iron deficiency. Most likely diagnosis?
Peptic ulcer disease (duodenal ulcer). Test for H. pylori; endoscopy if alarm features.
🍽️ What is the site of maximum absorption for iron and folate?
Duodenum and proximal jejunum. Coeliac disease affects proximal mucosa → iron deficiency.
🦷 A 4-year-old with dysphagia, food impaction, and failure to thrive. Endoscopy shows concentric rings, furrows. Biopsy hallmark?
≥15 eosinophils per high-power field (eosinophilic esophagitis).
🧪 Non-invasive test to confirm H. pylori eradication after therapy?
Stool antigen test (4 weeks after antibiotics). Urea breath test also reliable.
⚠️ A 2-month-old with bilious vomiting and abdominal distension. Immediate next step?
Supine and erect abdominal X-ray to exclude malrotation with volvulus or intestinal obstruction.
🩺 What immune structure is most characteristic of small intestine defence?
Peyer’s patches (aggregated lymphoid nodules) in ileum; secretory IgA prevents pathogen adherence.
💊 First-line PPI dose for moderate-severe GORD in an infant?
Omeprazole 1–2 mg/kg/day (max 40 mg/day) once daily; may split dose if refractory.
🧪 A child with chronic diarrhoea, bloating, and elevated anti-tTG. Diagnosis?
Coeliac disease (small intestinal villous atrophy). Confirmed by duodenal biopsy.
🔪 A 6-year-old with cyclic vomiting attacks, normal exam, and positive family history of migraine. Treatment?
Prophylaxis: amitriptyline, cyproheptadine, or topiramate. Avoid triggers.