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  • More common in boys (4:1)
  • Often a maternal family history
  • Increased risk if siblings were affected
  • Erythromycin exposure in first few weeks of life


There is a functional obstruction of the pyloric sphincter, as the muscle in this region hypertrophies. This ultimately results in almost complete obstruction.

Clinical features

Presents at 2-7 weeks of age – and is not related to gestational age

Projectile vomiting (non-bile stained), in an otherwise well child

  • Typically occurs after each feed
  • This increases in severity and frequency as the child continues to grow
  • It really is projectile! – hits the walls / ceiling in some cases
  • The child is usually otherwise well – in contrast to other causes of vomiting in neonates
  • Obvious continued hunger despite vomiting. Only in the later stages when they are severely dehydrated will the child lose interest in feeding.
  • Hypochloraemic alkalosis (metabolic alkalosis due to vomiting), and Hypokalaemia
  • Failure to thrive / weight loss / poor weight gain
  • DehydrationCheck for:
    • Skin turgor
    • Sunken eyes
    • Moist mucous membranes
  • When dehydration is marked and severe, the child may not be keen to feed


  • Milk Test – Give the child a normal milk feed. A wave of peristalsis should be visible across the abdomen from left to right
  • Examination
  • Pyloric olive – a 2-3cm mass that can sometimes be felt in the URQ. Usually mobile
  • USS – Often used to confirm diagnosis of sphincter hyperplasia. Pylroci muscle usually >4mm thick (normal <2cm)
  • Barium Meal – may be rarely used in cases when diagnosis is not certain. It will shows the string sign of an elongated and narrowed pyloric sphincter.


  • Initial Management – Correct fluid and electrolyte imbalances (if present)
  • Surgery – Ramstedt pyloromyotomy – the excessive muscle is removed, but all gastric mucosa is left intact. Post-operatively the baby can usually feed normally within 24 hours of surgery



  • Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
  • Oxford Handbook of General Practice. 3rd Ed. (2010) Simon, C., Everitt, H., van Drop, F.
  • Beers, MH., Porter RS., Jones, TV., Kaplan JL., Berkwits, M. The Merck Manual of Diagnosis and Therapy

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