What happened, in summary

A 70-year-old man with poorly controlled type 2 diabetes had a 30-mm early gastric cancer found during screening endoscopy. The lesion was removed by endoscopic submucosal dissection. Pathology showed a well-differentiated intramucosal cancer measuring 28 × 19 mm, with negative margins and no lymphovascular invasion. No perforation or immediate bleeding was seen, and he went home 5 days later.

Twenty-eight days after the procedure, he returned with gradually worsening upper abdominal pain and fever. CT showed an abscess beneath the left lobe of the liver but no free air or obvious gastric-wall perforation. Antibiotics were started, but 3 days later the abscess ruptured into the abdominal cavity and signs of peritoneal irritation developed.

Laparoscopic surgery was performed to wash out the abdomen, remove infected material and place a drain. Klebsiella pneumoniae grew from the abscess. Endoscopy afterward showed that the stomach ulcer created by the cancer resection was healing slowly, but no perforation site was found. The abscess was considered a delayed complication of the endoscopic resection, with poor diabetes control likely contributing to slow healing. He subsequently recovered and was discharged home 27 days after admission.