A 3-week-old baby boy is brought in by his parents with projectile vomiting. He is vomiting approximately half and hour after every feed but remains hungry. On examination he appears dehydrated and you can palpate an olive sized mass in the upper abdomen.

  1. What is the most likely diagnosis?
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This child is highly likely to have a diagnosis of infantile hypertrophic pyloric stenosis.

Infantile hypertrophic pyloric stenosis is caused by diffuse hypertrophy and hyperplasia of the smooth muscle of the antrum of the stomach. This results in narrowing of the pyloric canal, which can then easily become obstructed.

It occurs in approximately 1 in 500 live births and is more common in males than females (M:F ratio = 4:1). First-born male children are believed to have the highest risk. It can also occur in adults, albeit very rarely.

The principal clinical feature of infantile hypertrophic pyloric stenosis is vomiting:

  • Onset of vomiting at 2-8 weeks of age
  • Vomiting is non-bilious and typically projectile
  • Vomiting usually occurs 30-60 minutes post feeding
  • The baby usually remains hungry after the vomiting
  • Occasionally haematemesis occurs


Other clinical features include:

  • Persistent hunger
  • Dehydration
  • Weight loss
  • Constipation


An enlarged pylorus, classically described as being olive shaped, is palpable in the right upper quadrant or epigastrium in approximately 95% of cases. This is most often present at the start of a feed.

  1. What acid-base disturbance would you expect to be present?
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The typical acid-base disturbance is a hypochloraemic metabolic alkalosis. This occurs due to loss of hydrogen and chloride ions in the vomitus, decreased secretion of pancreatic bicarbonate. The increased bicarbonate ions presented to the distal tubule of the kidney results in the production of alkaline urine. Hyponatraemia and hypokalaemia are also usually present.

  1. What is the investigation of choice?
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The investigation of choice is ultrasound scanning, which is both reliable and easy to perform. This has now replaced barium studies as the investigation of choice.

  1. How should this case be managed?
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Initial management is with fluid resuscitation. This should be guided by the weight and degree of dehydration. Any electrolyte imbalance should also be corrected.

The definitive management is surgical, with the procedure of choice usually being a Ramstedt pyloromyotomy. Laparoscopic pyloromyotomy is also performed and is an effective alternative where suitable facilities are available. The prognosis is excellent unless there is a delay in diagnosis and initiation of treatment.

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