[A new methodology for the preoperative localization of occult insulinomas]

In patients with hypoglycemic syndrome, preoperative localization of the insulinoma highly contributes to surgical removal. When the ultrasonography, computed tomography, magnetic resonance and pancreatic angiography fail to visualize the tumor, they are called occult insulinomas (OI). In this paper we describe the results of a new diagnostic method to localize OI, performed in 5 patients with hypoglycemic syndrome secondary to endogenous hyperinsulinism. In four out of five patients, computed tomography, magnetic resonance and angiography failed to show any tumor. In just one single case, these imaging methods showed the pancreatic tumor. All patients were studied by selective intraarterial pancreatic stimulation (SIPS): a) infusion of calcium gluconate (0.025 mEq/kg) in each artery that supplies the pancreas: gastroduodenal, superior mesenteric and splenic arteries as well as the hepatic artery; b) insulin venous sampling in the right supra-hepatic vein at 30 and 60 seconds after arterial stimulation (in one patient an additional sample at 90 seconds was obtained). The study was considered pathologic when the gradient (basal vs post-stimulus) increased at least 100%.

In all five patients a pathological gradient was found. The suspected preoperative localization of the tumor was confirmed at surgery in four cases. The anatomopathologic examination revealed insulinoma in four cases and malignant insulinoma in the remaining. It is concluded that the results of this preliminary experience show the usefulness of SIPS in the preoperative localization of occult insulinomas.