Clinical Case 079: Is it Pyloric stenosis?

Picking the baby with pyloric stenosis from all the refluxing, positing and normal kids can be tricky.  In GP land this is a really common presentation: a new mum with a kid who “spews” after feeding.  We know that the vast majority of these kids will have no pathology, but you really don’t want to  miss an important diagnosis like hypertrophic pyloric stenosis (HPS) or a more sinister GI obstruction, sepsis or other badness.  So I thought I would tell you all about my all time favourite PS diagnosis and have a look at the recent evidence for the diagnosis and management of HPS.

This baby ticked all the boxes :

  • he was a boy (~80 % of HPS in males),
  • His symptoms started around 4 weeks age, and presented at 5 weeks (classic age)
  • he was a few weeks premature (commoner in premmy babies – and they present relatively younger),
  • his mother described a progressive history of increasingly voluminous and forceful vomiting over the past week, this was non-bilious.
  • He was constantly hungry and wanting to feed immediately after spewing.
  • He had lost weight i.e. was not thriving as is often the case in overfed babies who get “overflow” vomits

My practice with the neonate presenting with vomiting is to observe a test feed in the ED or the rooms and watch to see what happens – usually you see a palmful of milky posit come up and can be reasonably reassured that this is likely normal “mum badge” production.

  • This little boy had a test feed and within 3 minutes he erupted like a volcano with a full feed being thrown about a foot in the air over mum, me and the bed – convincing.

The classical triad of HPS is:

  • a palpable “olive” or “tumour” in the RUQ, 48%
  • visible peristalsis ~ 25 %
  • Hypochloremic (hypokalemic) metabolic alkalosis
    • Interestingly hemetemesis was present in 16% at diagnosis – not a traditional symptom of HPS
    • Seeing one component of the triad is common, seeing all 3 is pretty rare – so do not rule out if your patient hasn’t a full deck of signs.

This triad is becoming a rare beast. Taylor et al (from Westmead in Sydney) published this paper in J of Paediatric Child Health in Jan 2013.  They showed that clinical diagnosis is now uncommon – less than 10%, with more reliance on imaging such as US and Ba studies.  Only about half had a “tumour” – which might be due to deskilling in us, or just earlier diagnosis?  Ultrasound seems like a good initial investigation as it is painless, non-invasive and has high sensitivity and specificity.  Here is a link to the SONOWORLD page on US for HPS – nice images.  This remains a techniclly tricky modality – so not one I would do myself in the ED and hang my hat upon.

The story continues:

So our little guy – what did examination show?  Well I could not feel a mass, the vomiting was very convincing….. but technology sealed the diagnosis!  The little guy’s grandfather was an Anaesthetist [in a hospital on the otherside of the country], who just happened to be doing a list for a Paediatric surgeon that morning.  Mum had videoed a clip of “visible peristalsis” after his morning feed and emailed it from her iPhone to her father, who showed it to the surgeon, who then called me just as I was observing the impressively projectile vomiting.  Slam dunk diagnosis!

So I placed an IV and took some blood for VBG and electrolytes.  Resuscitation and electrolyte correction are the cornerstones of initial management.

IV fluid choice – well this is one where saline is probably a better option.  Ringer’s or Hartman’s may make things worse as you are increasing the bicarbonate and may precipitate apnoeas. However, it is common to have low K+, so you might need to add some of that in as well depending on the severity and what your labs show.

The VBG showed an alkalosis with a high bicarb and an increased CO2 [as expected in HPS].  Beware the presence of a metabolic acidosis might indicate severe hypovolemia and low perfusion – so this might muddy the acid-base picture in the severely dehydrated baby.  Presumably they will have a raised lactate to go along with the acidosis?

So now – here is the conundrum.  This boy needs to get to a surgeon to have his pyloromyotomy soonish, yet he is at risk for apnoeas.  So when is it safe to transfer him?

Can we predict who might have apnoeas? Well I couldn’t find any hard evidence but most protocols suggest the risk is lower once the HCO3 is under 30 mmol.  So that seems like a good target.  I think in the really small and premature babies the risk would be higher – so you might need a super-specialist advice on that one.

Alright – that is all I know about pyloric stenosis.  It can be tough to pick the true PS out of the crowd of spewing kids.  Our classical triad is not the norm, however I would advocte the use of US early as it is pretty good and there is no real downside.

Let me know your thoughts.

Casey

4 Comments

Add a Comment

Your email address will not be published.