Pyloric Stenosis

Pyloric stenosis is also known as hypertrophic pyloric stenosis, characterised by thickening of the pyloric muscles in the stomach, leading to gastric outlet obstruction, impaired gastric emptying and vomiting in babies.

Causes and Risk Factors

Pyloric stenosis is the most common cause of needing surgical intervention in the first 6 months of life ^[Ref]

Exact underlying cause is unknown, risk factors include: ^[Ref1][Ref2]

• Males (4:1)
• First-born infants
• Family history
• Maternal and perinatal factors
  • Maternal smoking
  • Preterm birth
  • Caesarean delivery
• Post-natal factors
  • Exposure to macrolide antibiotics (e.g. erythromycin)
  • Bottle feeding

Clinical Manifestation

Age at presentation: 3-8 weeks of life ^[Ref]

Classic presentation of projectile vomiting ^[Ref1][Ref2]

• Vomiting is non-bilious, and may appear milky (as the pyloric obstruction occurs proximal to the entry of bile into the duodenum)
• Vomiting occurs immediately after feeding (may happen after every feed or intermittently)
• The infant remains hungry after vomiting (“hungry baby”)

Signs of pyloric stenosis: ^[Ref1][Ref2]

• Pathognomonic “olive” mass on palpation
  • A firm, non-tender, hard epigastric or RUQ mass (as a result of the hypertrophic pylorus)
  • Seen in 60-80% of infants
• Visible gastric peristalsis (visible gastric peristaltic waves passing from left to right across the upper abdomen)

Complications from vomiting + ineffective feeding: ^[Ref1][Ref2]

• Fewer wet nappies
• Weight loss / dropping weight centiles
• Failure to thrive
• Signs of dehydration (e.g. sunken fontanelles, sunken eyes, dry mucous membrane, cold peripheries, ↑ CRT) is usually seen in established or late-presenting cases

Investigation and Diagnosis

Pyloric stenosis should be suspected in an <2 m/o infant with: ^{[NICE NG1]}

• Frequent, forceful (projectile) vomiting, or
• Progressively worsening or forceful vomiting of feeds

Arrange urgent specialist hospital assessment

Initial Work Up

If pyloric stenosis is suspected, perform ALL the following: ^{[NHS GGC]}

• Assess weight
• Assess for signs of dehydration
• Capillary blood gas

Diagnostic Test

Diagnostic test of choice: ultrasound ^{[NHS GGC]}

• Classic “target sign” – thickened pyloric muscle ring surrounding the central mucosal layer (seen on the transverse plane) ^[Ref]
• Thickened pyloric muscle wall
• Lengthened pyloric canal
• Lack of gastric emptying – no fluid or gas passing through the pyloric canal into the duodenum

Management

Initial Management

Initial management aims to restore fluid balance and correct any metabolic disturbances: ^{[NHS GGC]}

• NBM
• IV fluids
  • Standard fluid prescription: 0.9% NaCl + 5% dextrose + potassium (100-150 mL/kg/day)
  • If there are clinical signs of dehydration → fluid bolus (10 mL/kg of 0.9% NaCl over <10 min)
• NG tube insertion (aspirate as required instead of free drainage)
• Consider PPIs (e.g. omeprazole) if there are blood-stained aspirates

Monitor with serial capillary blood gas / blood test (at least 12-hourly) until the metabolic alkalosis and electrolyte abnormalities are corrected ^{[NHS GGC]}

Definitive Management

Definitive management: surgical correction ^{[NHS GGC]}

• Pyloromyotomy (Ramstedt’s operation)
• Laparoscopic or open approach

Post-operative management: ^{[NHS GGC]}

• Remove NG tube
• Stop IV fluids
• Restart feeds when clinically appropriate

References