A case of immune checkpoint inhibitor-associated gastroenteritis detected by ultrasonography.

While immune checkpoint inhibitors (ICIs) have antitumor effects, they also have characteristic side effects, including colitis. However, gastritis has rarely been reported. We report a case of a patient with lung adenocarcinoma who presented with epigastric pain and diarrhea following pembrolizumab administration. Sonography of the abdomen demonstrated diffuse, although mild, gastric wall thickening (mainly in the submucosa), as well as a slight decrease in echogenicity throughout the gastric wall. While the mucosal surface was relatively smooth, color Doppler examination showed increased vascularity. Esophagogastroduodenoscopy and pathological examination confirmed the diagnosis of ICI-related gastroenteritis.