Mr. Lim, a 47-year-old man, presented with abdominal pain and diarrhea. Endoscopy revealed a duodenal ulcer and CT scan showed a 3cm pancreatic head mass suspected to be a gastrinoma. Laboratory tests found highly elevated gastrin and basal gastric acid levels consistent with Zollinger-Ellison Syndrome. Further tests demonstrated increased gastrin response to secretin stimulation, confirming a gastrin-secreting pancreatic tumor as the cause of his symptoms. Complications of ZES include peptic ulcers, diarrhea from excess acid inactivating pancreatic enzymes, and potential malignant spread of gastrinomas. Omeprazole was prescribed to reduce gastric acid levels and treat his