Insulinoma: diagnosis and localization procedures

A 26-year-old Hispanic woman presented for evaluation of hypoglycemia documented by plasma glucose of 38mg/dl. A supervised 72-hour fasting test showed a plasma glucose of 30 mg/dl, insulin of 11 ulU/ml, proinsulin of 16.8 pmol/L and C-peptide 2.3 ng/ml after 16 hours of fasting. Sulfonylurea screen was negative. MRI showed a 12mm mass in the head of the pancreas. The tumor was resected and pathology was consistent with an insulinoma. The patient has been asymptomatic postoperatively with no hypoglycemia on repeat fasting. We reviewed here the different modalities for preoperative localization of insulinoma.