Islet cell hyperplasia localized by pancreatic vein catheterization and insulin radioimmunoassay

A patient with organic hypoglycemia but with normal pancreatic arteriography was investigated with pancreatic vein catheterization for insulin immunoassay. Very high insulin concentrations (1, 130 micronU/ml) were found in a vein draining part of the pancreatic tail. Even though no tumor was found at operation, distal hemipancreatectomy was performed according to the assay findings. Histology and immunohistochemistry revealed a localized islet hyperplasia.