Introduction Catheter-based ambulatory monitoring to study gastro-oesophageal reflux (GER) is conventionally performed using a single pH sensor to detect intra-oesophageal acid. A less-often used system is a dual pH catheter, allowing simultaneous measurement of oesophageal and gastric pH. In our tertiary referral GI Physiology Unit, we routinely perform pHmetry or impedance-pHmetry using dual-pH sensor probes for concurrent oesophageal and gastric pH monitoring. Aim: To evaluate the additional diagnostic yield associated with using gastric pHmetry analysis during gastro-oesophageal reflux pH monitoring.

Method We retrospectively evaluated 2916 dual pH reflux studies done in our unit between 2009 and 2016 (pH-only or combined pH-impedance). In patients having ‘off’ PPI studies we looked for evidence of prolonged gastric pH buffering by meals that provoked further investigation with gastric emptying study, and for evidence of gastric achlorhydria.

In patients having ‘on’ PPI studies (for investigation of reflux refractory to PPI therapy) we evaluated whether inadequate gastric acid suppression (defined as gastric pH >4 for>50% of study period¹) could be seen on gastric pH monitoring.

Results 271 patients (9.4%) had studies performed ‘on’ the patient’s current proton pump inhibitor therapy (PPI) to investigate refractory GORD symptoms. 150/271 patients (55% of ‘on PPI’ studies) were shown to require escalation of treatment, due to inadequacy of gastric acid suppression (defined as gastric pH >4 for>50% of ¹) The gastric pH profile further contributed to the diagnostic workup in 135 patients studied ‘off’ acid suppressive therapy (5% of ‘off PPI’ cohort). 111 patients with overlapping symptoms of reflux and dyspepsia had prolonged postprandial elevation of gastric pH period study², prompting suspicion of gastroparesis. 72/111 underwent formal gastric emptying testing on 13C-octanoic acid breath test or scintigraphy, and 59/72 were confirmed to have delayed gastric emptying. Finally, latent gastric achlorhydria (gastric pH >4 for the entire study period) was discovered in 24 patients, thus explaining PPI failure and obviating the need to continue PPI for presumed acid reflux.

Conclusion For small extra cost (£5 per study in the UK) and no additional labour (automated gastric pH analysis), intragastric pH profiling in routine GER monitoring contributes to diagnostic yield and subsequent clinical management in three ways:

1) assessing adequacy of gastric acid suppression ‘on PPI’ in the event of persistent symptoms;

2) suggesting underlying gastroparesis in reflux-dyspepsia overlap syndromes;

3) revealing latent gastric achlorhydria.

References

1. . Bonapace ES, et al. Dig Dis Sci. 2000Jan;45(1):34–9.

2. . Ooi & Glasinovic, et al. UEG Journal 2016;4(5S):A157–A720.A497.[P0991]

Disclosure of Interest J. Ooi: None Declared, P Woodland Conflict with: Reckitt Benckiser (Hull, UK), E Glasinovic: None Declared, K Nikaki: None Declared, S Sonmez: None Declared, E Yazaki: None Declared, D Sifrim Conflict with: Reckitt Benckiser (Hull, UK); Sandhill Scientific (CO, USA)