Pyloric Stenosis

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | Referral

Definition

Pyloric stenosis, or hypertrophic pyloric stenosis, is a condition in infants where the pylorus (muscle between the stomach and small intestine) becomes abnormally thickened, causing gastric outlet obstruction. It commonly presents between 2 to 6 weeks of age.

Aetiology

The exact cause is unknown, but it is thought to result from genetic and environmental factors leading to abnormal thickening of the pyloric muscle.

Pathophysiology

• Hypertrophy of the circular muscle fibres of the pylorus leads to narrowing of the gastric outlet.
• This causes delayed gastric emptying, resulting in forceful, projectile vomiting.
• Prolonged vomiting leads to electrolyte imbalance, metabolic alkalosis, and dehydration.

Risk factors

• Male gender (4:1 male-to-female ratio).
• Firstborn child.
• Family history of pyloric stenosis.
• Exposure to macrolide antibiotics (e.g., erythromycin) in early infancy.
• Formula feeding (weak association).

Signs and symptoms

Symptoms:

• Projectile non-bilious vomiting after feeding (often described as forceful).
• Persistent hunger despite vomiting.
• Weight loss or failure to thrive.
• Dehydration (reduced wet nappies, sunken fontanelle).

Signs:

• Visible peristalsis in the upper abdomen (after feeding).
• Palpable "olive-shaped" mass in the right upper quadrant or epigastrium (best felt after vomiting).
• Signs of dehydration (e.g., dry mucous membranes, poor skin turgor).

Investigations

• Blood tests:
  • Hypochloraemic, hypokalaemic metabolic alkalosis (low chloride, low potassium, high bicarbonate).
  • Raised urea and creatinine if dehydrated.
• Ultrasound (gold standard):
  • Thickened pyloric muscle (>3 mm).
  • Elongated pyloric channel (>15 mm).
• Plain abdominal X-ray: May show a distended stomach with little air in the intestines (rarely needed).

Management

1. Initial Stabilisation:

• Rehydration: IV fluids with normal saline and potassium supplementation to correct dehydration and electrolyte imbalances.
• Monitor electrolytes: regular blood tests to track progress.

2. Definitive Treatment:

• Surgical pyloromyotomy (Ramstedt’s procedure):
  • A longitudinal incision is made through the hypertrophied pyloric muscle to relieve the obstruction.
  • Performed laparoscopically or via open surgery.
  • High success rate with minimal complications.

Referral

• Urgent referral to paediatric surgery if pyloric stenosis is suspected.
• Early referral to paediatricians for stabilisation and diagnosis confirmation.