The patient is most likely to have Zollinger-Ellison syndrome (ZES), a condition caused by a gastrinoma. In 25% of cases, ZES is associated with multiple endocrine neoplasia type 1 (MEN-1). Clinical features of MEN-1 include gastrinoma or other islet cell tumor, hyperparathyroidism, and anterior pituitary tumors. ZES should be especially considered in a patient with multiple, refractory, or recurrent peptic ulcer disease, especially if accompanied by diarrhea or hypercalcemia. Diarrhea is often a predominant symptom and is caused by the large volume of acid that inactivates pancreatic lipase and damages the absorptive mucosa of the proximal gut. Tests to diagnose ZES include serum gastrin radioimmunoassay, secretin stimulation test, somatostatin receptor scintigraphy, and endoscopic ultrasound. Almost all gastrinomas contain somatostatin receptors on the gastrin cells and somatostatin scintigraphy using [111In-DPTA-Dphe1]-octreotide is considered the initial localization study of choice. It has 71% sensitivity and 86% specificity for primary tumors and 92% sensitivity for detection of metastatic disease.
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