24-h recording of intragastric pH: technical aspects and clinical relevance.
BACKGROUND
Information about gastric acid secretion and gastric acidity can be obtained using several techniques but, presently, continuous intragastric pH recording is probably the one applied most frequently. This paper aims to review the technical aspects and some important applications of intragastric pH monitoring in research and clinical practice.


METHODS
Literature review.


RESULTS
Most studies on intragastric pH are performed with either glass or antimony electrodes. Optimal measurement of 24-h intragastric pH requires accurate calibration of the pH measuring system, exact positioning of the pH electrodes, and a sufficient sample rate. Depending on the aim of the study the results of intragastric pH monitoring are expressed either as median H+ activity or as median pH values. Gastric acidity shows a circadian rhythm, modified by buffering meals and nocturnal duodenogastric reflux. In health, age, gender and smoking habits are known to influence gastric acidity. In duodenal ulcer disease an increased gastric acidity is found and in patients with gastric ulcer gastric acidity is decreased. In GERD, no relation between reflux oesophagitis and gastric acidity is found. Helicobacter pylori affects intragastric pH most pronounced during acid inhibitory therapy, both in DU patients and in healthy subjects. In the absence of H. pylori the effect of proton-pump inhibitors on intragastric pH is much less than in the presence of the microorganism, whereas the effect of ranitidine on intragastric pH is barely affected by the H. pylori status.


CONCLUSIONS
Despite some limitations, intragastric pH monitoring provides important information about gastric acidity.
van Herwaarden
M A
MA
University Hospital Utrecht, Dept. of Gastroenterology, The Netherlands.
Samsom
M
M
Smout
A J
AJ
D002940:Circadian Rhythm / Q000502:physiology; D004381:Duodenal Ulcer / Q000378:metabolism; D004942:Esophagitis, Peptic / Q000378:metabolism; D005744:Gastric Acid / Q000378:metabolism*; D005753:Gastric Mucosa / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D018670:Monitoring, Ambulatory / Q000379:methods*; D012680:Sensitivity and Specificity; D013276:Stomach Ulcer / Q000378:metabolism