Abstract
A 31-year-old man with inpaired consciousness and urinary and fecal incontinence was admitted to hospital. Based on his low blood glucose (BG) levels (29 mg/dl), he was diagnosed as being in a hypoglycemic coma. The patient recovered after receiving an intravenous infusion of glucose.Although insulinoma was suspected as a cause of the hypoglycemia, hyperinsulinemia was never demonstrated.In other words, the patient's immunoreactive insulin (IRI) levels were always lower than 10μU/ml, and his IRI/BGratio was never higher than 0.5.However, the patient's plasma proinsulin levels were markedly elevated at 89.3 pmol/L (the normal range is 2.9-13.1 pmol/L).An intra-arterial calcium infusion was performed to determine if a pancreatic islet cell tumor was present.The calcium was infused into the celiac artery, and a sample was taken through the portal vein by percutaneous transhepatic portal catheterization.During this test, a marked rise in IRI levels was observed at the confluent point of the portal-splenic vein.Moreover, a selective celiac angiography revealed a tumor stain at the pancreatic uncus. The patient was diagnosed as having insulinoma, and surgery was performed to enucleate the tumor. After surgery, the patient's plasma proinsulin levels fell to a normal value of 6.4pmol/L and the hypoglycemic symptoms disappeared.The low IRI and high proinsulin levels observed this case are relatively rare among cases of insulinomas.Intra-arterial calcium infusion with venous sampling can be a useful procedure for the detection of insulinoma.
