Volume 121, Issue 4, Pages 775-783 (October 2001) Unbuffered highly acidic gastric juice exists at the gastroesophageal junction after a meal  Jonathan Fletcher, Angela Wirz, Joanne Young, Ramsey Vallance, Kenneth E.L. McColl  Gastroenterology  Volume 121, Issue 4, Pages 775-783 (October 2001) DOI: 10.1053/gast.2001.27997 Copyright © 2001 American Gastroenterological Association Terms and Conditions

Fig. 1 Refluxate minimum pH and corresponding gastric minimum pH under fasting conditions and during meal buffering. Gastric minimum pH is the median value of the lowest gastric pH measured during reflux episodes per patient; refluxate minimum pH is the median value of the lowest esophageal pH measured during reflux episodes per patient. ●, Analyzed retrospectively; ○, analyzed prospectively. Gastroenterology 2001 121, 775-783DOI: (10.1053/gast.2001.27997) Copyright © 2001 American Gastroenterological Association Terms and Conditions

Fig. 2 The distance from the nostril at which the pH probe changed from reading a low gastric pH to a neutral esophageal pH under fasting and postprandial conditions. The distances recorded in each individual are correct to 1 cm. Median values are indicated by horizontal bars. Postprandial distances are less than fasting distances (P < 0.05). Gastroenterology 2001 121, 775-783DOI: (10.1053/gast.2001.27997) Copyright © 2001 American Gastroenterological Association Terms and Conditions

Fig. 3 Median pH min for each electrode position in the stomach and esophagus after a meal. The electrode positions were set 1 cm apart. pH min is the lowest pH recorded over 1 minute at each electrode position. *pH greater than at the electrode position marked †(P < 0.01). Gastroenterology 2001 121, 775-783DOI: (10.1053/gast.2001.27997) Copyright © 2001 American Gastroenterological Association Terms and Conditions

Fig. 4 Example of a pH tracing recorded from an electrode during the catheter pull-through technique in 1 subject while fasting and again after a meal. The postprandial recording shows a region of high acidity corresponding to the location of the pH step-up point observed under fasting conditions. Gastroenterology 2001 121, 775-783DOI: (10.1053/gast.2001.27997) Copyright © 2001 American Gastroenterological Association Terms and Conditions

Fig. 5 Mean pH at each electrode position during the postprandial pull-through of both the proximal and distal electrode in 1 individual. A pocket of unbuffered acid is seen in the region of the GEJ consistently with both electrodes. Gastroenterology 2001 121, 775-783DOI: (10.1053/gast.2001.27997) Copyright © 2001 American Gastroenterological Association Terms and Conditions

Fig. 6 Distance from the nostril to the squamocolumnar junction and pH step-up before and after a meal in the 10 patients who had their squamocolumnar junctions marked with clips. The squamocolumnar junction was measured using the radiograph of the distal electrode position in 9 subjects (the pH step-up point of the proximal electrode was not identified by radiography). The pH step-up was measured using both electrodes in 9 subjects and 1 electrode in 1 subject. *Distance from nostril to postprandial pH step-up less than under fasting conditions (P < 0.01). Gastroenterology 2001 121, 775-783DOI: (10.1053/gast.2001.27997) Copyright © 2001 American Gastroenterological Association Terms and Conditions

Fig. 7 pH recorded from an electrode at the top and bottom of a beaker containing a homogenized meal onto which acid gastric juice has been poured. (A) Before and (B) after agitation of the mixture for 1 minute. Gastroenterology 2001 121, 775-783DOI: (10.1053/gast.2001.27997) Copyright © 2001 American Gastroenterological Association Terms and Conditions