Pyloric Stenosis

Definition, Epidemiology & Pathophysiology - Tiny Tummy Trouble

• Definition: Gastric outlet obstruction (GOO) from progressive hypertrophy & hyperplasia of the pyloric sphincter's circular muscle.
• Epidemiology:
  • Incidence: 1-3/1000 live births (Caucasians ↑).
  • M:F ratio 4-5:1; common in first-born males.
  • Peak age: 3-6 weeks (rare >12 weeks).
  • Risk factors: Family history, neonatal erythromycin/azithromycin exposure, maternal smoking.
• Pathophysiology:
  • Etiology: Multifactorial (genetic predisposition, environmental factors, neuronal dysfunction e.g., ↓NO synthase, ↑gastrin).
  • Leads to thickened, elongated, firm pylorus (palpable "olive" in ~50-70%). 📌 Olive-mass, Little Infant Vomits Everything (OLIVE).

  ⭐ Pyloric stenosis is the most common cause of intestinal obstruction in infancy requiring surgery. oka

Clinical Features & Classic Signs - The Projectile Puzzle

• Onset: 2-8 weeks (up to 12 weeks); M:F 4:1.
• Vomiting:
  • Non-bilious, projectile (forceful, non-staining).
  • Progressive, occurs post-feed, increases over days.
  • Infant hungry after emesis ("hungry vomiter"), eager to refeed.
• Palpable "Olive":
  • Firm, mobile, ~1-2 cm smooth muscle mass in RUQ/epigastrium.
  • Pathognomonic; best felt post-vomiting, with relaxed abdomen.
• Other Signs:
  • Visible gastric peristalsis (L→R waves).
  • Dehydration (↓ urine output, sunken fontanelle, poor skin turgor).
  • Weight loss / failure to thrive despite good appetite.
  • Jaundice (~5%; unconjugated hyperbilirubinemia, resolves post-op).

⭐ Classic triad: Projectile non-bilious vomiting, palpable "olive" mass, and visible gastric peristalsis.

Diagnosis & Investigations - Unmasking the Muscle

• Clinical Clues:
  • Non-bilious projectile vomiting (typically 3-6 weeks).
  • Palpable "olive" mass in RUQ/epigastrium (pathognomonic, felt in ~50-70%).
• Laboratory Findings:
  • Classic: Hypochloremic, hypokalemic metabolic alkalosis.
  • Paradoxical aciduria (late finding).
  • Serum: ↓Cl⁻ (<98 mEq/L), ↓K⁺ (<3.5 mEq/L), ↑HCO₃⁻ (>26 mEq/L).
• Imaging - The Decider:
  • Ultrasound (USG): Gold Standard
    • Pyloric Muscle Thickness (PMT): >3-4 mm (most accurate)
    • Pyloric Canal Length (PCL): >14-16 mm
    • Pyloric Diameter: >12 mm
    • Signs: "Antral nipple", "Cervix sign", "Target sign".
  • Upper GI Contrast (Barium Meal): (If USG inconclusive)
    • "String sign" (narrowed pyloric channel).
    • "Shoulder sign" (pylorus indents antrum).
    • "Mushroom sign" (pylorus indents duodenum).

⭐ The single most accurate ultrasonographic criterion for diagnosing pyloric stenosis is a pyloric muscle thickness (PMT) of >3 mm (some sources say >4 mm).

Management & Complications - The Surgical Solution

• Pre-operative Stabilization (KEY):

  • IV Fluids: Correct dehydration, hypochloremic, hypokalemic metabolic alkalosis.
    • 0.9% NaCl bolus (20 mL/kg).
    • Maintenance: D5 0.45% NaCl + KCl (20 mEq/L).
  • NG tube for gastric decompression.
  • Aim: Urine output >1-2 mL/kg/hr, Cl⁻ >85, K⁺ >3.5, HCO₃⁻ <30 mEq/L.

• Definitive Surgery: Fredet-Ramstedt Pyloromyotomy

  • Longitudinal myotomy of hypertrophied circular muscle; mucosa intact.
  • Open (RUQ incision) or laparoscopic.

• Post-operative Management:

  • Feeding: Start 4-6 hrs post-op, advance as tolerated.
  • Analgesia.

• Complications:

  • Intra-op: Mucosal perforation (repair + omental patch).
  • Post-op:
    • Persistent emesis: Incomplete myotomy (most common), edema, GERD.
    • Wound infection, dehiscence.

⭐ High-Yield: The most common reason for persistent vomiting after pyloromyotomy is an incomplete myotomy.

High‑Yield Points - ⚡ Biggest Takeaways

• Non-bilious projectile vomiting in infants aged 2-8 weeks is the cardinal symptom.
• A palpable "olive" mass in the epigastrium is a classic physical finding.
• Hypochloremic, hypokalemic metabolic alkalosis is the characteristic electrolyte disturbance.
• Ultrasound: pyloric muscle thickness >4 mm, channel length >16 mm are diagnostic.
• Definitive treatment is Ramstedt pyloromyotomy after initial fluid resuscitation.
• Increased risk in first-born males and with postnatal erythromycin exposure.