Clinical Practice Guidelines

Pyloric stenosis

  • See also: Gastroenteritis


    Hypertrophic Pyloric Stenosis (HPS) is due to progressive thickening of the circular muscle of the pylorus. This leads to gastric outlet narrowing.

    The condition usually presents between 2 and 6 weeks of age.

    Risk factors:

    • Male
    • Firstborn 
    • Caucasian
    • Parental history of HPS (higher if mother affected)



    • Vomiting 
      • progressively more forceful and may be projectile
      • non-bilious
      • blood stained in up to 10% of cases
    • Usually don't have diarrhoea
    • Often hungry afterwards
    • Weight loss or inadequate weight gain 


    • Assess degree of dehydration
    • Weigh and plot on growth chart with previous weights if available
    • Look for jaundice (1-2% of infants with HPS)
    • Look for gastric peristalsis (waves of muscle contraction across the abdomen passing from the left upper quadrant to the right lower quadrant).
    • Feel for a pyloric mass (best felt in the right upper quadrant with the infant supine. Approximates the size and shape of an olive. Best felt from left side. Wait for several minutes.)
    • Signs may be more obvious following a feed


    • Take blood for FBE, U&E, Acid-Base, Glucose (bilirubin if jaundice present)
      Hypochloraemic Hypokalaemic Metabolic Alkalosis may be seen.
    • If diagnosis not yet established, abdominal ultrasound is the investigation of choice (95% sensitive).


    • Fluid resuscitation may be necessary with 10-20ml/kg boluses of normal saline, for patients with moderate to severe dehydration
    • Commence IV Fluids (0.9% sodium chloride (normal saline) and 5% or 10% glucose + 10mmol KCl / 500mls) at 100mls/kg/day initially. Review after 4-6 hours (see below).
    • Stop oral feeds
    • Insert a nasogastric tube if vomiting continues despite stopping feeds. Replace nasogastric losses with IV normal saline 
    • Repeat U&E, Acid-Base 4-6 hourly initially and adjust fluid accordingly. The aim for most infants should be to fully correct fluid and electrolyte deficits within 48 hours.
    • Initial KCl may be required if significant hypokalaemia
    • Replace deficit, in addition to maintenance, in those infants who are clinically dehydrated (weight is a good marker of the degree of dehydration)


    • Correction of HPS is not an emergency, and should not be undertaken until normal electrolytes and pH have been restored and the infant is rehydrated
    • It is particularly important to fully correct serum bicarbonate before theatre because of the risk of hypoventilation/ apnoeas post-operatively in the setting of metabolic alkalosis.
    • Operation is Ramstedt's Pyloromyotomy (may be done laparoscopically in some cases)
    • Feeding is usually restarted within 6 hours post-op. Some children will continue to vomit for several days. Infants are usually discharged within 3 days.
    • Re-stenosis can occur, but is uncommon (1-2%).
    • See Parent handout

    Pyloric Stenosis flowchart 

    Pyloric Stenosis flowchart

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