Objective: Long term gastric pH monitoring has been proposed to diagnose abnormal duodenogastric reflux. This study analyses the in situ reproducibility of continuous intragastric pH measurements to assess the influence of artifactual factors in producing spontaneous variations of pH values that might be frequently misinterpreted as episodes of duodenogastric reflux.
Methods: The investigation was carried out in 301 endoscopically proven duodenal ulcer patients (87 female, 214 male, mean age 46 yr). Each patient underwent 24-h gastric pH monitoring with two closely adjacent pH electrodes whose tips were about 2 mm apart. The two simultaneous pH tracings obtained from each patient were analyzed with regard to the number, characteristics, and discrepancies of unexpected alkalinization waves over the entire circadian cycle.
Results: The simultaneous pH tracings of the two-channel datalogger we used ran almost superimposed for more than 23 h in 224 out of 301 (74%) duodenal ulcer patients. Major discrepancies between the two pH tracings of each recording were obtained in the remaining cases (77/301 = 26%). The most frequent event was represented by unexpected alkalinization waves that occurred mainly during nighttime and were recorded by only one of the two simultaneously measuring electrodes. As few as 16/244 (7%) patients showed synchronous, unexpected alkalinization waves that one might eventually consider to be duodenogastric refluxes.
Conclusions: It is rather common that only one of two closely adjacent pH electrodes placed within the stomach measures longlasting pH elevations, particularly during the nocturnal period. This discrepancy is due to a poor in situ reproducibility of simultaneous pH recordings and indicates that pH readings might be influenced by interference and artifacts. Thus, the frequent differences between two simultaneous pH readings and the indirect measurement of the backflow of duodenal contents with long term gastric pH-metry do not allow us to rely on this technique to diagnose duodenogastric reflux.