Pyloric stenosis diagnosis and pyloromyotomy

🫒 Pathophysiology - The Olive Pit Stop

• Progressive hypertrophy and hyperplasia of the pyloric muscularis propria (both circular and longitudinal layers).
• This narrows the pyloric channel, leading to a functional gastric outlet obstruction.
• Etiology is multifactorial, with a key association being neonatal macrolide exposure (e.g., erythromycin).
• 📌 Mnemonic: The pylorus becomes a muscular "pit stop" too thick for food to pass.

⭐ The thickened muscle creates the pathognomonic physical finding: a palpable, firm, mobile, ~2 cm "olive-shaped" mass in the epigastrium.

🤮 Clinical Manifestations - Projectile Problems

• Classic Onset: Healthy infant (often first-born male) at 2-8 weeks of age.
• Hallmark Vomiting:
  • Projectile, non-bilious emesis, typically 30-60 min after feeding.
  • Infant is a "hungry vomiter," eager to feed again immediately.
• Physical Exam Findings:
  • Palpable, firm, mobile "olive-shaped" mass in the epigastrium/RUQ.
  • Visible peristaltic waves moving left-to-right across the upper abdomen.
• Consequences:
  • Dehydration (↓ skin turgor, sunken fontanelle).
  • Failure to thrive or weight loss.

⭐ The classic metabolic disturbance is a hypokalemic, hypochloremic metabolic alkalosis. Paradoxical aciduria may occur as kidneys excrete H+ to conserve K+.

🫒 Diagnosis - Finding the Olive

• Physical Exam: A palpable, firm, mobile "olive-sized" mass in the RUQ/epigastrium is pathognomonic but often absent.
• Labs: Reveal hypokalemic, hypochloremic metabolic alkalosis from emesis of gastric $HCl$. Paradoxical aciduria may occur as kidneys conserve $K^+$ at the expense of $H^+$.
• Imaging:
  • Abdominal Ultrasound (US): Test of choice.
    • Pyloric muscle thickness > 4 mm
    • Channel length > 16 mm
  • Upper GI Series (if US non-diagnostic): Shows "string sign."

⭐ Pre-op management is key: Correct dehydration and electrolyte abnormalities with IV fluids before pyloromyotomy. Surgery is not an emergency.

🔪 Management - Pre-Op to Pyloromyotomy

• Pre-operative Stabilization (CRUCIAL):

  • Correct dehydration & hypochloremic, hypokalemic metabolic alkalosis ($↓Cl⁻, ↓K⁺, ↑HCO₃⁻$).
  • IV fluids: Start with Normal Saline (NS) bolus.
  • Maintenance: D5 1/2 NS + KCl (add K⁺ only after urination confirmed).
  • Surgical clearance: Cl⁻ > 85 mEq/L, HCO₃⁻ < 30 mEq/L, adequate urine output.

• Definitive Treatment: Pyloromyotomy

  • Ramstedt pyloromyotomy: Longitudinal incision of the hypertrophied pyloric muscle, leaving mucosa intact.
  • Can be done open or laparoscopically.

⭐ Pyloromyotomy is urgent, but NOT an emergency. Surgery is delayed until fluid and electrolyte abnormalities are corrected to reduce anesthetic risk.

⚠️ Complications - Post-Op Pitfalls

• Persistent Vomiting: Most common post-op issue.
  • Causes: Incomplete pyloromyotomy, GERD, gastritis.
• Mucosal Perforation: Intra-op complication requiring immediate repair.
• Wound Infection/Dehiscence: Standard surgical site risks.

⭐ Persistent emesis for 24-48h post-op is common due to gastric atony. If vomiting continues >5 days, suspect incomplete myotomy.

⚡ Biggest Takeaways

• Classic triad: Non-bilious projectile vomiting, a palpable "olive-like" mass, and visible peristalsis in a 2-6 week old infant.
• Diagnosis: Abdominal ultrasound is the gold standard, showing a thickened (>4 mm) and elongated (>14 mm) pylorus.
• Lab hallmark: Hypokalemic, hypochloremic metabolic alkalosis with paradoxical aciduria due to volume contraction and RAAS activation.
• Pre-op management is critical: First, correct dehydration and electrolytes with IV fluids (NS, then D5 ½ NS + KCl).
• Definitive treatment: Ramstedt pyloromyotomy, an incision of the hypertrophied pyloric muscle.