We report a case of hyperplastic polyp prolapsing into the duodenum, which caused the ball valve syndrome. A 65-year-old woman was admitted because of epigastric pain and vomiting after eating. CT of the upper abdomen showed a tumor within the duodenal bulb. Endoscopic examination revealed transpyloric prolapse caused by the typeIV gastric polyp. The polyp was pushed back into the stomach. Polypectomy was performed. The tumor was 25×20 mm in size. Histological findings were consistent with a hyperplastic gastric foveolar polyp. After treatment, the patient’s symptoms resolved. She has not shown any recurrence of the symptoms until now.
