Makindo Medical Notes

🍼🤮 Hypertrophic pyloric stenosis (HPS) – Infants typically develop hypochloraemic, hypokalaemic metabolic alkalosis. Diagnosis is confirmed with ultrasound (USS) 🖥️.

📖 About

• A common cause of projectile, non-bilious vomiting in infants 🚼.
• Caused by hypertrophy of the pyloric muscle → gastric outflow obstruction.
• Often presents as a surgical emergency but prognosis is excellent once treated.

🧬 Aetiology

• 👦 More common in first-born male infants.
• 📈 Incidence: ~2–4 per 1000 live births.
• 👩‍👦 Family history (especially maternal side) suggests genetic predisposition.
• Mechanism: pyloric muscle hypertrophy + hyperplasia → narrowing of pyloric channel.

🩺 Clinical Features

👉 To palpate the “olive”: stand on the baby’s left side, palpate with the left hand along the lateral border of the right rectus in the RUQ, ideally during a feed.

• ⏰ Usually presents between 2–7 weeks of age.
• 🤮 Non-bilious, projectile vomiting shortly after feeds.
• 🍽️ Infant remains hungry after vomiting ("hungry vomiter").
• 🚫 No diarrhoea – constipation is common; may pass “starvation stools”.
• ⚠️ Large-volume vomiting within minutes of feeding → weight loss, dehydration.
• 👶 Infant often alert, anxious, and malnourished if untreated.
• ✋ Palpable olive-shaped mass in RUQ = classic sign.
• 👀 Visible peristalsis may be seen across the abdomen after a feed.

🖼️ Image

🔎 Investigations

• Bloods: Classic finding = hypochloraemic, hypokalaemic metabolic alkalosis 🧪. Hypokalaemia usually develops after 2–3 weeks of persistent vomiting.
• Ultrasound (USS): 📏 Diagnostic test of choice – pyloric thickness >3mm and length >15mm = HPS.
• Barium meal: Rarely used; may show “string sign” but generally unnecessary.

💊 Management

• Initial Stabilisation:
  • 💧 IV fluid resuscitation + electrolyte correction (replace K⁺ and Cl⁻ until Cl⁻ >90 mmol/L).
  • 🛑 Delay surgery until metabolic derangements are corrected (to avoid anaesthetic risk).
  • 🧴 NG tube decompression if severe gastric distension.
• Definitive Treatment:
  • ✂️ Ramstedt’s pyloromyotomy = standard surgical cure. Muscle split along pylorus, mucosa left intact.
  • 🚼 Usually performed laparoscopically in modern practice.
  • 📈 Excellent prognosis – most feed normally within 24–48h post-op.

⚠️ Complications if Untreated

• 💧 Severe dehydration & electrolyte imbalance
• 📉 Failure to thrive
• 🫀 Shock & metabolic alkalosis complications (e.g., hypoventilation, seizures)

🧑‍🏫 Exam Tip

The triad of hypertrophic pyloric stenosis = 1️⃣ Non-bilious projectile vomiting, 2️⃣ Palpable olive-shaped mass, 3️⃣ Visible gastric peristalsis. Always link the metabolic alkalosis (low Cl⁻, low K⁺, raised HCO₃⁻) to the underlying repeated vomiting of gastric contents. This is a classic finals OSCE favourite 🎯.

Cases — Infantile Hypertrophic Pyloric Stenosis

• Case 1 — Classic presentation 🍼: A 6-week-old first-born boy presents with 2 weeks of progressively worsening non-bilious, projectile vomiting after feeds. Exam: visible gastric peristalsis and an olive-shaped mass in the right upper quadrant. Bloods: hypochloraemic, hypokalaemic metabolic alkalosis. Diagnosis: classic hypertrophic pyloric stenosis. Managed with IV fluid and electrolyte correction followed by Ramstedt pyloromyotomy.
• Case 2 — Failure to thrive 📉: A 7-week-old girl presents with poor weight gain, constipation, and frequent vomiting. She is dehydrated with sunken eyes and dry mucous membranes. Blood gas: metabolic alkalosis. Ultrasound: elongated, thickened pylorus. Diagnosis: pyloric stenosis with dehydration and failure to thrive. Managed with urgent fluid/electrolyte replacement and planned surgical pyloromyotomy.
• Case 3 — Atypical late presentation ⚠️: A 12-week-old boy presents with persistent vomiting and irritability. Exam: abdominal distension and metabolic alkalosis. History of delayed diagnosis due to atypical age. Ultrasound confirms pyloric stenosis. Diagnosis: delayed diagnosis of pyloric stenosis. Managed with fluid resuscitation, correction of electrolytes, and surgery.

Teaching Point 🩺: Infantile hypertrophic pyloric stenosis usually presents at 2–8 weeks of life, more common in first-born males. Key features: projectile non-bilious vomiting, palpable olive-shaped mass, visible peristalsis. Biochemical hallmark: hypochloraemic, hypokalaemic metabolic alkalosis. Management = correct fluids/electrolytes first, then Ramstedt pyloromyotomy.