This will be a single-centre, randomised, endoscopist-blind, parallel-group study in patients who are scheduled endoscopic submucosal dissection (ESD) for gastric mucosal lesion. The primary objective is to observe whether a regimen of 7-day oral esomeprazole premedication can alleviate intraoperative bleeding in patients scheduled for ESD due to gastric mucosal lesions.

Inclusion Criteria:

• Ability to understand and the willingness to sign a written informed consent document.
• Female or male aged ≥18 years.
• Patients must have gastric mucosal lesion that are eligible for ESD indications (Japanese Gastric Cancer Association 2011), including early gastric cancer, polyps, adenoma, and precancerous/suspected lesions diagnosed by endoscopy.

Exclusion Criteria:

• Malignancy or other advanced disease with a life expectancy of < 6 months as judged by the investigator.
• The ASA classification of physical status ≥ 4 as judged by the investigator.
• Severe hepatic disease or renal disease
• Ability to understand and the willingness to sign a written informed consent document.
• Major cardiovascular event at enrollment or within 3 months prior to enrollment such as stroke, myocardial infarction, or hospitalization for treatment of unstable angina pectoris as judged by the investigator.
• Haemorrhagic disorder.
• Patients who had a history of gastrectomy or a recurrent lesion.
• Known or suspected hypersensitivity to any component of any PPI .
• Planned treatment with: warfarin (including other vitamin K antagonists), cisapride, phenytoin, atazanavir, nelfinavir, digoxin, methotrexate, clopidogrel, tacrolimus, theophylline, lidocaine, nifedipine.
• Pregnancy, planned pregnancy or lactation. Women of childbearing potential must use reliable and medically accepted methods of birth control, as judged by the investigator.
• Known or suspected alcohol, drug or medication abuse.
• Any condition associated with poor compliance as judged by the investigator.
• Participation in any study involving administration of an investigational product or device within the preceding 14 days prior to enrollment.
• Involvement in the planning and conduct of the study. Previous enrollment in the present study.

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