Heidelberg Gastric pH Testing

The digestive tract is analogous to an assembly line.  There are several anatomical and functional portions each which has specific tasks to complete before passing the resulting material to the next section.  All digestion starts in the stomach.  If that does not proceed well, the intestinal tract is going to be given food that has not had the initial phase of digestion completed, which affects all subsequent digestive activity.  If the acidic stomach environment does not complete the initial breakdown phase called hydrolysis, the intestinal enzymes often cannot adequately complete the middle and final portions of digestion.

As could be anticipated from the above discussion it is important to look at stomach phase digestion to understand the broader digestive synergistic process.  The Heidelberg Gastric pH Test is ideally suited for this task.The Heildelberg test uses a telemetry capsule to transmit pH signals to a receiver, which is placed over the stomach.


The capsule is swallowed with water, and once it reaches the stomach it sends pH readings to the receiver on the surface of the stomach.  The capsule is tethered to a piece of surgical thread to hold it in the stomach preventing it from quickly passing into the small intestine.  This allows stomach pH readings to be taken repeatedly over the 1-2 hours needed for the test as will be described in the next paragraph..

The base level acidity of the stomach should be about 1.5, which is moderately acidic (Point 1 below).  To test the capacity of the stomach during digestion a small amount of sodium bicarbonate in water is swallowed which quickly increases stomach pH to 7 similar to what happens as food enters the stomach (Point 2).  More stomach acid production should return the pH to 1.5 within 22 minutes (Point 3).  In true excessive acid production this may occur in 8-10 minutes.

In hypochlorhydria, or too little acid production, the stomach may take 30 minutes or more to re-acidify to pH of 1.5.

Up to 3 alkaline challenges can be done as in early hypochlorhydria proper reacidification may occur within 22 minutes, but it will not occur with the second or third challenge.  These persons usually have less severe symptoms and may only have them with larger meals.  In more severe hypochlorhydria the stomach may have had a baseline pH of 4 or more, which is far too little acidity to digest.

When food passes out of the lower stomach through the pyloric valve into the small intestine, it is mixed with bile and sodium biocarbonate to neutralize the acidity. This allows the small intestinal enzymes to then work as they need a more alkaline environment. If the pyloric valve does not close well allowing Bile acids to reflux into the stomach, some bicarbonate will also enter causing upward spikes in the pH graph as shown below.

Properly treating reflux symptoms starts with precisely knowing what is causing them.  The Heidelberg Gastric pH test is an important tool in this process.


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