Changes in overnight fasting intragastric pH show poor correlation with duodenogastric bile reflux in normal subjects

Spontaneous rises in intragastric pH are a common phenomenon in patients and normal subjects who undergo prolonged ambulatory pH monitoring; however, controversy exists over their etiology. Some investigators have postulated that these events are secondary to duodenogastric bile reflux (DGBR), and others have implicated increased salivation or increased esophageal bicarbonate production. The advent of a fiberoptic system that reliably identifies the presence of bilirubin has made it feasible to qualitatively detect DGBR. We used this technology along with simultaneous ambulatory intragastric pH monitoring to evaluate the relationship between DGBR and rises in intragastric pH in normal subjects.

We studied five normal subjects for a 15-h overnight period with simultaneous intragastric pH and bilirubin monitoring. The probes were sutured together so that the pH electrode lay adjacent to the fiberoptic bilirubin sensor, then passed transnasally into the fundus of the stomach. Subjects were fasted for the entire study. Data were obtained by plotting all intragastric pH values (recorded every 4 s) and their corresponding intragastric bilirubin absorbance units (recorded every 8 s) at 5-min intervals from the beginning to the end of the study for each of the five subjects (n = 903).

Regression analysis of the data showed poor correlation (r = 0.26) between intragastric pH and intragastric bilirubin absorbance.

Rises in intragastric pH do not predict the presence of bile in normal subjects. In addition, DGBR usually does not cause alkaline shifts of intragastric pH. Although further studies are needed to fully elucidate the etiology of spontaneous rises in intragastric pH, we believe that the measurement of "alkaline reflux" with ambulatory intragastric pH monitoring alone is an outdated technique and that the Bilitec 2000 should become the standard technique for the detection of intraluminal bile.