Gastric hypersensitivity induced by oesophageal acid infusion in healthy volunteers

Distal oesophageal acid exposure has been shown to increase visceral sensitivity of the proximal oesophagus via central sensitization. Here we evaluated whether acidification of the distal oesophagus also affects the sensorimotor function of the proximal stomach. A gastric barostat study combined with a 30-min acid (HCl 0.15 mol L(-1)) or saline infusion in the distal oesophagus was performed in 18 healthy volunteers. Gastric and cutaneous sensitivity was assessed before and up to 2 h after the start of infusion. Directly after acid infusion, but not after saline, the threshold for discomfort decreased (-6.4 +/- 1.7 vs 0.4 +/- 0.4 mmHg; P = 0.028) and distension-induced symptoms increased significantly compared with the baseline (122 +/- 49% vs -3 +/- 9%). Cutaneous sensitivity remained unaffected by acid infusion. In contrast, when the infused liquid was aspirated 3 cm more distally, at the level of the lower oesophageal sphincter, the effect of acid infusion on gastric sensitivity was abolished and the increase in distension-induced symptoms was reduced (61 +/- 24%). Distal oesophageal acid infusion induces visceral hypersensitivity without affecting somatic sensitivity arguing against a similar mechanism of central sensitization as observed in non-cardiac chest pain. As reduction of the acid load to the stomach prevented this effect, our findings indicate that either gastric and/or duodenal acidification is involved. It should be emphasized though that aspiration from distal oesophagus may have attenuated the effect by reducing the acid-exposed area or by reducing the contact time