Objective To clarify the effectiveness of second-look endoscopy (SLE) at preventing bleeding after gastric endoscopic submucosal dissection (ESD).

Design A multicentre prospective randomised controlled non-inferiority trial was conducted at five referral institutions across Japan. Patients with a solitary gastric neoplasm were enrolled. Exclusion criteria were previous oesophagogastric surgery or radiation therapy; perforation and the administration of antithrombotics, steroids or non-steroidal anti-inflammatory drugs. Patients were assigned to the SLE group or the non-SLE group by a computer-generated random sequence after ESD and were treated perioperatively with a proton pump inhibitor. SLE was performed one day after ESD. The primary endpoint was post-ESD bleeding, defined as an endoscopically proven haemorrhage. The trial had the power to detect a non-inferiority criterion of 7% between the groups.

Results From February 2012 to February 2013, 130 and 132 patients were assigned to the SLE and the non-SLE groups, respectively. All patients were included in the intention-to-treat analysis of the primary endpoint. Post-ESD bleeding occurred in seven patients with (5.4%) SLE and five patients with (3.8%) non-SLE (risk difference −1.6% (95% CI −6.7 to 3.5); p_{non-inferiority}<0.001), meeting the non-inferiority criterion. All 12 patients with post-ESD bleeding and one patient with a delayed perforation were successfully managed with conservative treatment.

Conclusions SLE after gastric ESD is not routinely recommended because it does not contribute to the prevention of post-ESD bleeding for patients with an average bleeding risk.

Trial registration number UMIN-CTR000007170.