Acid reflux and its associated symptoms occur most frequently following the ingestion of a meal. This observation presented a dilemma as intragastric pH is at its least acidic following eating due to the buffering effect of the food. However, the observation by Fletcher et al that the proximal cardia region of the stomach escapes the buffering effect of the meal provided a rational explanation for the acidic nature of the postprandial refluxate.1 The zone of high acidity detected in the proximal stomach after a meal has been termed the acid pocket.

The presence of the acid pocket has been confirmed by a substantial number of investigators and by a variety of different investigative techniques. The latter have included pH pull-through,2–4 multiple static pH electrodes3 and single photon emission CT (SPECT) of the stomach following intravenous injection of [^99MTc]pertechnetate which is secreted by the acid-secreting cells of the gastric mucosa.5

It had been suggested that the acid pocket might represent only a film of acid lining the proximal stomach without any significant volume.6 In the current issue of Gut (see page 441) Beaumont et al placed a catheter at the anatomical site of the acid pocket and aspirated 50–70 ml of gastric juice pH 1.7–2.5 during the postprandial period.7 They were also able to show that the SPECT imaging of …