Introduction: Insulinoma is an uncommon pancreatic neuro-endocrine tumour characterized by hyperinsulinemic hypoglycemia. It is important to surgically remove this tumor as it can cause potentially lethal hypoglycemia. The conventional imaging techniques have limitations in accurate pre-operative localization of small duodeno-pancreatic neuroendocrine tumors. The high spatial resolution of endoscopic ultrasound (EUS) permits better detection of such small tumors. We describe a report of 12 patients supporting the above observation. Results: 12 patients with insulinoma who had surgery at our institution were reviewed. (7 enucleation, 3 distal pancreatectomy, 2 unresectable). One of the patient with unresectable tumor was locally invasive and other had vascular invasion not detected on EUS prior to surgery. 9 of the tumors were located in the tail, 2 in head of pancreas and 2 in the body of pancreas (one patient had two tumors). The mean size of tumors was 2.72×2.18cm. Three patients had surgical resection done before EUS was available at our center. Pre-operative CT scan failed to localize the tumor in these patients. EUS done in the other nine patients accurately localized the tumor prior to surgical resection. Immunological staining on fine needle aspiration obtained at the time of EUS was consistent with insulinoma and revealed malignancy in one patient. One patient had two tumors which were detected on EUS prior to surgery. Conclusion: Our experience with 12 patients is in accordance with previous reports claiming EUS to be the method of choice for preoperative imaging and localization of pancreatic islet cell tumors. Preoperative evaluation is necessary for planning pancreatic surgery to assess for resectability
