Phlegmonous gastritis is a rare inflammatory lesion in which bacterial infection occurs in the gastric wall. A 92-year-old man was admitted to the medical ward due to early gastric cancer. The patient received endoscopic submucosal dissection (ESD), and he complained of sudden-onset upper abdominal pain the day after ESD. On physical examination he showed rebound tenderness in the upper abdomen. The white blood cell count was 16,100/μl, and an abdominal CT-SCAN showed diffuse and irregular thickening of the gastric wall. At emergency operation, a subtotal gastrectomy was performed, and the patient had an uneventful recovery.
