Case report: phlegmonous gastritis after endoscopic mucosal resection for a Helicobacter pylori-naïve foveolar-type gastric adenoma with a raspberry-like appearance.

A 66-year-old man underwent endoscopic mucosal resection (EMR) for a small foveolar-type gastric adenoma with a raspberry-like appearance in Helicobacter pylori-naïve gastric mucosa. The following day, he developed high fever and septic shock with hemodynamic instability without abdominal pain. Contrast-enhanced computed tomography revealed localized gastric wall thickening from the fundus to the body, consistent with phlegmonous gastritis (PG) after EMR complicated by septic shock with hemodynamic instability. He was successfully managed conservatively with meropenem. Streptococcus parasanguinis and Streptococcus salivarius were subsequently isolated from the gastric juice.PG is a rare but potentially fatal bacterial infection of the gastric wall that progresses rapidly. High fever is the most consistent finding, whereas abdominal pain may be absent, delaying recognition. Delayed diagnosis often leads to systemic sepsis and contributes to its high mortality. The main route of infection is direct mucosal invasion, often after endoscopic procedures, and most cases develop within one day of the intervention, with surgery frequently required. When high fever develops within a few days after endoscopic intervention, PG should be considered in the differential diagnosis, even in the absence of abdominal pain, to ensure timely management.