The origin of nocturnal intragastric pH rises in healthy subjects.
BACKGROUND
Duodenogastric reflux (DGR) can produce transient increases in gastric luminal pH. It has been proposed that intragastric pH-metry is a reliable method for the detection of DGR. Our aim was to test the hypothesis that nocturnal increases in antral pH are due solely to DGR.


METHODS
Gastric pH was monitored overnight using two glass pH electrodes, one in the antrum adjacent to the tip of a nasogastric tube and one in the corpus. Scheduled antral aspirations were performed hourly to determine base-line concentrations of total bile acids (TBA; a marker of DGR) and thiocyanate (SCN; a marker of swallowed saliva). Additional, triggered aspirations were performed if antral pH exceeded 3.0 for 1 min or more (PHAP; period of high antral pH). TBA and SCN were considered to be increased if they exceeded the 90th percentile of values determined in scheduled aspirates (TBA, 0.88 mM; SCN, 0.67 mM).


RESULTS
In 28 of the 62 samples whose aspiration was triggered by a PHAP the pH was less than 3.0, and the sample was not considered to be representative. In the remaining 34 samples the antral luminal pH and the sample pH were concordant; TBA alone was increased in 6 samples, SCN alone was increased in 6 samples, and TBA and SCN were both increased in another 3 samples. Thus, DGR and swallowed saliva alone or in combination accounted for only 15 (45%) of the PHAP in which adequate gastric samples were obtained.


CONCLUSIONS
Samples of gastric antral contents often do not reflect accurately the acidity of gastric fluid in contact with a luminal antral pH electrode. Nocturnal increases in antral pH, detected by a luminal electrode, are frequently due to mechanisms other than duodenogastric reflux or swallowed saliva. Thus, antral pH-metry is not suitable for monitoring the occurrence of duodenogastric reflux.
Division of Gastroenterology, CHUV, Lausanne, Switzerland.
E F
EF
Verdú
R
R
Fraser
G M
GM
Murphy
A L
AL
Blum
D
D
Armstrong
D000328:Adult; D001647:Bile Acids and Salts / Q000378:metabolism; D002940:Circadian Rhythm; D003679:Deglutition; D004383:Duodenogastric Reflux / Q000378:metabolism; D005260:Female; D005744:Gastric Acid / Q000378:metabolism*; D005745:Gastric Acidity Determination; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D011706:Pyloric Antrum / Q000378:metabolism; D012463:Saliva / Q000378:metabolism; D013861:Thiocyanates
D001647:Bile Acids and Salts; D013861:Thiocyanates; C031760:thiocyanate