It is because hiatus hernia is not the cause of GERD. If it was, we wouldn't be here, together in our misery.
Anyone who says HH causes GERD doesn't know much about
this condition or at best looks at it in a very simplistic and inaccurate way.
Unfortunately, science still hasn't found the exact mechanism(s) that are causing the LES (Lower Esophageal Sphincter) to stop working properly. We just lack the technology that is sophisticated enough to measure many things on a small scale in our bodies over longer periods of time.
Hiatus Hernia can make the condition worse in some cases, but it's not the cause. If it was, then we would just be fixing hernias by stitching diaphragms and be OK after that, and there would be no need for doing wraps with Nissen Fundoplication and other messy workarounds.
Case in point: I fixed my hernia + done partial Nissen Fundoplication. I now have much worse reflux and symptoms than I ever had before the surgery (the worst mistake in my life, but I had to try) even though my hernia is now fixed. I really hoped it was hernia - nope.
My philosophical answer: We want a simple answer, that we could easily point at. But that doesn't seem to be case here. There might be several causes, or worse - there might be several different causes of which each consists of many different factors. Just look how many different variations of symptoms and responses to treatments there are among us with some form of reflux disease.
Some of my theories:
- It's of neurological origin, some kind of dysfunction of an autonomous nervous system.
- There is a possible autoimmune component where esophagus reacts stronger to reflux than it's the case with normal people, causing quicker and stronger inflammation. Or there is no damage at all but high perception of burning/pain.
- Than there is the microbiome, about
which the research field is exploding in the past years - which may explain why some people get worse symptoms on PPI which are proven to be messing with the diversity of our gut population.
All the treatments available today deal with symptoms and not the cause - why? Because we don't have a clue what the cause is. Or if there are several different causes. And we don't have a clue how to fix LES directly - or to identify and treat the nerves or neuro-chemical network that controls the digestive system (including esophagus) that controls LES functioning.
There are people with hernia that don't have GERD, and there are people who have GERD but they don't have hernia. We don't really know what percentage of people in the world have hiatus hernia, because they are mostly asymptomatic, and people don't usually do upper endoscopy unless they have bad symptoms. And even when they do, smaller ones are not always caught.
However, it seems like most people with GERD have hernia too. But correlation is not the same as causation. It certainly can be a piece of the puzzle that will, hopefully, one day be solved.
I hope sooner, because this is a living hell.
In short, you haven't gotten it wrong, just nobody knows it yet.
That, of course, shouldn't keep us from searching for what works for us and keep fighting for improving our symptoms and daily wellbeing. Even a little improvement means the world with these kind of chronic conditions.
Hope this helped a little