Pyloric stenosis typically presents in the second to fourth weeks of life with vomiting, although rarely may present later at up to four months. It is caused by hypertrophy of the circular muscles of the pylorus.

Epidemiology

• incidence of 4 per 1,000 live births
• 4 times more common in males
• 10-15% of infants have a positive family history
• first-borns are more commonly affected

PC

• Presents in first few weeks of life with a hungry baby that is thin, pail, failing to thrive
• 'projectile' vomiting, typically 30 minutes after a feed. Happens as the powerful peristalsis of the stomach ends up sending the food up the oeseophegus as a result of a blocked pylorus
• constipation and dehydration may also be present

Examination - a palpable mass may be present in the RUQ of the abdomen. Feels like a large olive, caused by hypertrophic muscle of the pylorus

Investigations

• ABG - hypochloraemic, hypokalaemic metabolic alkalosis due to persistent vomiting (losing HCl)
  • Can also have a lactic acidosi picture later in the clinical course as the dehydration worsens
• Diagnosis is most commonly made by ultrasound - thickened pylorus

Management

Correct electrolyte abnormalities before surgery