Infant pyloric stenosis – some theories about its cause

What causes pyloric stenosis in babies and what does this mean for the way it is treated?

Prof Dr Ian M Rogers, a senior practising and teaching pediatric surgeon, has said: There can be few clinical conditions more fascinating and less understood than hypertrophic pyloric stenosis of infancy (IHPS).

Some years ago Dr Rogers reflected on a life of treating babies with infant hypertrophic pyloric stenosis (“IHPS” or “PS”).  I found his open accessible medical journal article on-line and in June 2012 summarised it (as well as I could as a lay person) for interested but non-academic readers – in other words for most of us who are or have been affected by this fairly common condition.

Mid-2012 Dr Rogers wrote a follow-up article, again in an open access medical journal, and he graciously sent me a copy.  I feel privileged that I can pass this material on also.

So what is the mechanism that causes a baby to start vomiting all its food just a few days or weeks or at most some months after birth?  Many websites tell us the causes of IHPS are likely many and are only very partly understood, that it’s best to operate promptly to relieve the blockage, and that there are usually no long-term after-effects.

a PS baby showing malnourishment

Dr Rogers reviews the various current theories about the cause(s) of PS and explains and argues for the theory that it is caused by inherited hyperacidity (excessive gastric acid levels in the stomach and/or duodenum).  The baby who inherits a normal level of gastric acidity will not reach acid levels severe enough to trigger over-development of the pyloric muscle despite the fact that high levels of gastrin (a hormone that controls the stomach’s gastric acid level) are normally secreted during the first 10 or so days after birth.  The possible danger will cease when gastrin secretion declines naturally with the baby’s age and as the pyloric canal becomes wider.  Genetic factors clearly must also be involved.

There are four theories for the cause of IHPS, and Dr Rogers summarizes the current basis of each and evaluates their status –

1)  Immunohistochemical abnormalities relate to cell and tissue chemistry and immunology.  We are told that  There are so many observed abnormalities that it is unlikely that any one of them is a prime mover in [causing IHPS.]…  Moreover, the abnormalities, if correct, may simply be the mechanism by which a sphincter [valve muscle] becomes hypertrophic [enlarged] as a result of frequent contraction.

2)  Genetic abnormalities: It is well recognised that a significant minority of PS cases occurs in particular families and that siblings are sometimes affected, so that there is clearly a genetic factor among other causes.  Gene mapping has confirmed this.  But the fact that our genes are not the single simple cause is shown by the incidence of PS in twins: although it is more commonly shared by identical twins than fraternal twins, it is far from even near universal.  The age at which PS appears also suggests it is not simply based on inheritance.

3)  An infectious cause might explain the fact that PS usually appears some weeks after birth, but despite several suspect bugs and diseases having been investigated, no link with any environmental trigger or infection has been found.

4)  The hyperacidity theory remains the only one that fits a list of distinctive facts about this condition.  Dr Rogers lists seven (which I quote) and adds two more –

1)  The male/female ratio of 4/1.

2)  The rapid disappearance of the tumour and the long–term cure after pyloromyotomy.

3)  The persistence of the tumour after gastroenterostomy [another surgical technique].

4)  The absence of the tumour at birth and the presence of the tumour at around 4 weeks of age.

5)  The known positive influence of a family history.

6)  The finding of high acid secretion in babies with IHPS and an increased incidence of duodenal ulcer dyspepsia and high volume outputs in long term survivors.

7)  An increased incidence with erythromycin therapy, an antibiotic which increases antral and pyloric contraction.

8)  The approximately 4 week period during which IHPS develops and does not return.

9)  Any condition which is cured by splitting a muscle is likely to be caused by the contraction of that muscle, especially in the light of fact #3.

Next post: more about the hyperacidity theory.

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3 thoughts on “Infant pyloric stenosis – some theories about its cause

  1. Wendy

    What a haunting photo! I’m sure I looked something like that. I weighed 4 pounds or less when I was finally operated on. Thanks for clarifying and simplifying the issues for us!

    Reply
  2. Fred Vanderbom

    Photos like this one keep reminding me how deeply our parents must have been affected by what we their little “pride and joy” went through before, during and after our surgery. Thanks for your response!

    Reply
  3. Pingback: Infant pyloric stenosis – closing in on its cause « Stories from the Survivors of early Surgery

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