Background and study aims White opaque substance (WOS) in gastric epithelial neoplasia is helpful for qualitative diagnosis of neoplasia. We hypothesized that WOS of neoplasia is strongly influenced by acid recovery after Helicobacter pylori eradication, similar to that of gastric intestinal metaplasia. The aim of this study was to investigate whether antacids increase the appearance of the WOS in H. pylori-eradicated neoplasia. Patients and methods A total of 38 gastric epithelial neoplasias (12 adenomas and 26 adenocarcinomas) detected after H. pylori eradication were retrospectively evaluated. Presence or absence of WOS was evaluated by magnifying endoscopy with narrow band imaging before and after antacid administration. The pH of collected gastric juice was also measured. Study endpoints were (1) prevalence of WOS in the neoplasia before and after antacid administration, and the histological difference (adenoma and adenocarcinoma); and (2) relationship between the prevalence of WOS and gastric juice pH. Results WOS prevalence increased from 0 % (0/38) to 44.8% (17/38) after antacid administration. WOS prevalence in adenomas was more significantly increased compared to that in adenocarcinomas (83.3 % vs 26.9 %, P = 0.0077). Prevalence of WOS in gastric neoplasias was only observed at neutral levels of gastric juice pH, and WOS was not observed at strong acidic levels. Conclusions Antacid administration may increase the appearance of WOS in gastric epithelial neoplasia (especially adenomas) detected after H. pylori eradication with acid recovery.

The Helicobacter pylori infection and functional dyspepsia are often coexisted. The effect of acotiamide, a drug for functional dyspepsia, on the result of Helicobacter pylori diagnosis has yet to be studied. We evaluated the influence of acotiamide on the results of Helicobacter pylori diagnosis in the 13 C urea breath test. Twenty patients with Helicobacter pylori positive functional dyspepsia were treated with 100 mg of acotiamide three times a day for two weeks. Changes in 13 C urea breath test were investi gated before and after administration, and two weeks after administration as the follow up period. The 13 C urea breath test and the medical questionnaire of modified frequency scale for the symptoms of gastroesophageal reflux disease were conducted at every period. Nineteen patients were included for analysis. No patients showed negative in 13 C urea breath test at Weeks 2 and 4. On the symptom scale, dyspepsia and total scores decreased from Week 0 to Week 2 and increased from Week 2 to Week 4, and the improvement rates of the dyspepsia score at Week 2 was 63%. In conclusion, we confirmed that acotiamide is unlikely to influence the result of 13 C urea breath test and it may improve the symptoms of functional dyspepsia during Helicobacter pylori eradication treatment.