context: Zollinger- Ellison syndrome ( ZES) is a disease of the gastrointestinal system. People who have ZES develop tumors known as gastrinomas in the pancreas and duodenum (the first section of the small intestine). The gastrinomas caused by ZES secrete the hormone gastrin. Because gastrin creates excessive stomach acid, 90 percent of patients with ZES develop stomach and duodenal ulcers. A person who has Zollinger- Ellison syndrome may have only one gastrinoma or may have several. Approximately 25% to 30% of ZES patients also have a genetic (inherited) disorder known as "multiple endocrine neoplasia type 1," which causes tumors in the pituitary and parathyroid glands. Another complication of ZES is that more than half of single gastrinomas are malignant (cancerous). These malignant gastrinomas can spread to other parts of the body, including the liver, lymph nodes, spleen, bones, or skin. People who have Zollinger- Ellison syndrome don't always have symptoms. When symptoms do occur, they include: Abdominal pain Burning pain in the abdomen Nausea Diarrhea Weight loss Vomiting Bleeding from the stomach Weakness Fatigue If your doctor suspects that you have ZES, he or she will perform a blood test to look for high levels of gastrin (the hormone secreted by gastrinomas). They may also perform tests to measure how much acid your stomach is producing. Your doctor may examine you for gastrinomas by performing an endoscopy. This procedure is done with a flexible, lighted tube (an endoscope) that looks at your esophagus, stomach and duodenum. This is often done with endoscopic ultrasound to see the tumor. Other tests your doctor might perform include a CT scan, a special type of X-ray that provides cross-sectional images of the body, a PET scan to locate tumors, and an octreotide scan to look for neuroendocrine tumor cells. Despite these tests, gastrinomas can be difficult to find. ZES is treated by reducing the amount of acid your stomach produces. Medications called proton pump inhibitors are usually prescribed. These drugs, which include lansoprazole ( Prevacid), omeprazole ( Prilosec, Zegerid), pantoprazole ( Protonix), dexlansoprazole ( Dexilant ), esomeprazole ( Nexium), and rabeprazole ( Aciphex), curb the production of stomach acid and allow the ulcers to heal. Treatment of ZES depends on whether the gastrinoma is sporadic or part of the inherited MEN I syndrome. While the latter is usually treated with acid suppression alone, sporadic gastrinomas are treated with acid suppression and surgical removal of the tumor. Somatostatin analogs such as octreotide, which suppresses hormone production, are also very good at controlling symptoms. If there is metastatic disease, you may be offered a combination of therapies including surgery, chemotherapy, or targeted drug therapy or radiation. Gastrinomas tend to grow slowly and are not always malignant. The five-year survival rate depends on whether tumors are cancerous and if they've spread. If they have not spread to the liver, the 5-year survival rate may be 90%. If surgery removes the gastrinoma, 20%-25% of patients are completely cured. If you have been treated for ZES, you should see your doctor on a regular basis to determine if the gastrinomas recur.