Transient hyperinsulinemic hypoglycemia of the newborn is relatively common and is seen frequently in infants of diabetic mothers.1 Erythroblastosis fetalis and Beckwith-Wiedemann syndrome are less common causes.2 By contrast, persistent hyperinsulinism is an uncommon cause of hypoglycemia in this age group.2 This form of hyperinsulinemia is often caused by nesidioblastosis, a diffuse disorder of the pancreas resulting from transformation of the pancreatic ductal tissue into insulin-producing islet cells, or rarely by an islet cell adenoma, a localized proliferation of the islets of Langerhans.2,3 In one review of 160 hyperinsulinemic infants, four adenomas were reported.4 Because an islet cell adenoma may be very small, attempts at diagnosis and localization by non-invasive techniques such as ultrasonography, computer tomography, and magnetic resonance imaging have usually been unsuccessful.
Defining ductal tissue
