The occult insulinoma operative localization by quick insulin radioimmunoassay.

Hypoglycemia secondary to organic hyperinsulinism in children can be caused by diffuse or localized pancreatic lesions. Differentiation between these two types of lesions is of utmost importance since the surgical approach will be different. Some tumors escape detection by all preoperative investigations including ultrasound, scintiscan, arteriography, and computerized tomography. We are reporting on a 12-year-old boy with organic hyperinsulinism in whom we were unable to localize a tumor preoperatively. Peroperative determination of insulin levels from a number of sites on the pancreas enabled us to localize an insulin-producing pancreatic adenoma. This technique can be done easily by catheterizing the splenic and portal vein through a branch of the splenic vein and by serial sampling at 2 cm intervals along the portal and splenic veins. Insulin levels at these sites were determined by quick double-antibody radioimmunoassay, which allows the determination of the insulin levels within 50 minutes after sampling. There was a perfect biochemic and anatomic correlation allowing us to perform a precise distal pancreatectomy. The technique can be used to localize pancreatic adenomas and to decide how much pancreas to remove in diffuse lesions avoiding "blind" pancreatectomies.