Effectiveness of bacteria reduction by irrigation of stomach with natural saline before endoscopic submucosal dissection and natural orifice transluminal endoscopic surgery

INTERVENTION: Irrigation of stomach and esophagus with 2000ml natural saline before ESD and NOTES No irrigation group CONDITION: Early gastric cancer, Gastric gastrointestinal stromal tumor PRIMARY OUTCOME: Efficacy of bacteria reduction by irrigation with natural saline during operation (ESD/NOTES) SECONDARY OUTCOME: WBC,CRP,BT,abdominal pain and aspiration pneumonia before and after ESD or NOTES INCLUSION CRITERIA: Fifty patients who are diagnosed with early gastric cancer or gastric GIST and are going to undergo ESD or NOTES