Short segment reflux: acid but no pocket?

I read the paper by Fletcher and colleagues with interest. (Gut 2004;53:168–73.) In their earlier study, the group reported the existence of an unbuffered acid pocket in 60% of study subjects which extended for approximately 2 cm (median length) in the postprandial period. Furthermore, when pre and postprandial pH step up distances were measured and correlated with clips fixed to the oesophagus, this acid pocket was localised to a region ‘‘just above’’ the squamocolumnar junction. It would be fair to infer then, that if a pH sensor was firmly implanted just above the squamocolumnar junction, it would record a prolonged acid reflux event in the postprandial state as the probe would be continuously bathed in acid from this reservoir. This is distinct from intermittent acid reflux events due to transient lower oesophageal sphincter relaxations or straining. In their more recent paper, greater acid exposure at the squamocolumnar junction was found compared with a site located 5 cm proximally (standardised recording point), which intuitively is not unexpected. This is especially so if DeMeesters hypothesis (which was alluded to in the manuscript) were to be accepted which proposes that the lower oesophageal sphincter, incorporating the squamocolumnar junction, opens up and becomes part of the stomach in the postprandial period. However, the authors have stated that there was no significant difference in the mean length of acid reflux episodes when both sites were compared. This appears to be at odds with the first study as one would have expected to observe a prolonged acid reflux event at the distal oesophageal recording site (that is, just above the squamocolumnar junction). However, this was not the case. In addition, presentation of data in the results section of the current study show a distinct lack of emphasis regarding the ‘‘acid pocket theory’’ which would lead one to assume that this was not observed. How do the authors reconcile these observations from their two studies?