Pyloric stenosis


These guidelines have been produced to guide clinical decision making for the medical, nursing and allied health staff of Perth Children’s Hospital. They are not strict protocols, and they do not replace the judgement of a senior clinician. Clinical common-sense should be applied at all times. These clinical guidelines should never be relied on as a substitute for proper assessment with respect to the particular circumstances of each case and the needs of each patient. Clinicians should also consider the local skill level available and their local area policies before following any guideline. 

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To guide staff with the assessment and management of pyloric stenosis.


  • Hypertrophic pyloric stenosis should be suspected in infants 3 to 6 weeks old with non-bilious vomiting after meals
  • Projectile vomiting is not always present
  • The typical age range is 3 to 6 weeks of age, but it is rare less than 10 days old and greater than 11 weeks
  • The incidence is 1:450
  • Males account for 85% of cases.

Risk factors

  • 20% have a positive family history



  • Gradual onset of non-bilious vomiting after feeds, becoming more forceful and sometimes projectile in nature
  • Vomitus may be lightly blood streaked
  • The child is typically hungry and irritable, and easily re-fed after a vomit
  • Failure to gain weight, or even weight loss is common.


  • Infant may be dehydrated
  • Visible gastric peristalsis, from left to right across the hypogastrium may be seen after a feed, just before the baby vomits
  • A pyloric mass ('pyloric tumour') may be felt below the liver edge just lateral to the edge of the right rectus abdomens muscle. It is best felt when the stomach is empty, just after a vomit.


  • Bloods - venous blood gas (VBG), UEC, FBC, BGL
  • VBG shows a metabolic alkalosis (hypochloraemic, hypokalemic alkalosis) in those with metabolic derangement
  • Abdominal ultrasound will usually confirm the diagnosis. Where this is not readily available plain abdominal films may show the 'single bubble' of gastric dilatation (with little or no air beyond the pylorus).

Differential diagnoses

  • Infants with pyloric stenosis are diagnosed earlier leading to fewer cases having classic symptoms, signs and metabolic derangements
  • Doctors treating infants need to be alert to non-classical presentations of pyloric stenosis
  • Pyloric stenosis should be considered as a differential diagnosis of all infants presenting with vomiting, particularly those under 3 months of age.


Initial management

  • Nil by mouth
  • Insert intravenous cannula (and take bloods)
  • Assess degree of dehydration
  • Commence intravenous fluids
    • 0.9% saline + 5% glucose + 20mml KCl (per 1000mL bag of fluid)
  • Fluid rate = maintenance plus calculated deficit over 24 hours
  • Nasogastric tubes (NGT) are not routinely inserted in the emergency department. The need for one will be assessed by the surgeons and can be inserted on the ward if required
  • Surgical team referral.

Further management

  • A pyloromyotomy is performed once the fluid and electrolyte derangement has been corrected
  • If a nasogastric tube is inserted all gastric losses via the NGT are replaced with Hartmann’s solution or 0.9% saline via a second infusion
  • A dose of intravenous Flucloxacillin will be given at the time of surgery. This does not need to be prescribed by emergency department staff.

Health information (for carers)


  1. Infantile hypertrophic pyloric stenosis: a review.Spicer RD Br J Surg. 1982;69(3):128. 
  2. Pyloric size in normal infants and in infants suspected of having hypertrophic pyloric stenosis.Hallam D, Hansen B, Bødker B, Klintorp S, Pedersen JF Acta Radiol. 1995;36(3):261. 
  3. Infantile hypertrophic pyloric stenosis: has anything changed?Taylor ND, Cass DT, Holland AJ J Paediatr Child Health. 2013 Jan;49(1):33-7. Epub 2012 Dec 2. 
  4. Pyloric stenosis: role of imaging.Hernanz-Schulman M Pediatr Radiol. 2009 Apr;39 Suppl 2:S134-9

Endorsed by:  Director, Emergency Department  Date:  Mar 2018

 Review date:   Mar 2021

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