A 64-year-old woman presented with a history of recurrent hypoglycemia. A prolonged fasting test revealed an increased "amended" insulin-glucose ratio. Transabdominal ultrasound (US), computed tomography (CT) scan, and magnetic resonance imaging (MRI) did not show abnormal results. An insulinoma was suspected based on a contrast-enhanced endoscopic US examination as well as a (68)gallium-DOTA-exendin-4 positron-emission tomography (PET)/CT. The diagnosis of an insulinoma was confirmed histologically after surgical removal of the tumor. Hypoglycemia did not occur during the postoperative period. The prolonged fasting test is the gold standard for the diagnosis of an insulinoma. Novel imaging procedures, such as contrast-enhanced endoscopic US or (68)gallium-DOTA-exendin-4 PET/CT are valuable additions to the diagnostic workup.
Keywords: Endoscopic ultrasonography; Exendin-4; Positron-emission tomography; Prolonged fasting test.