A NEW METHODOLOGY FOR PREOPERATIVE LOCALI ZATION OF OCCULT INSULINOMAS

In patients with hypoglycemic syndrome, preoperative localization of t he insulinoma highly contributes to surgical removal. When the ultraso nography, computed tomography, magnetic resonance and pancreatic angio graphy fail to visualize the tumor, they are called occult insulinomas (OI). In this paper we describe the results of a new diagnostic metho d to localize OI, performed formed in 5 patients with hypoglycemic syn drome secondary to endogenous hyperinsulinism. In four out of five pat ients, computed tomography, magnetic resonance and angiography failed to show any tumor. In just one single case, these imaging methods show ed the pancreatic tumor. All patients were studied by selective intraa rterial pancreatic stimulation (SIPS): a) infusion of calcium gluconat e (0.025 mEq/kg) in each artery that supplies the pancreas: gastroduod enal, superior mesenteric and splenic arteries as well as the hepatic artery; bf insulin Venous sampling in the right supra-hepatic vein at 30 and 60 seconds after arterial stimulation (in one patient an additi onal sample at 90 seconds was obtained). The study was considered path ologic when the gradient (basal vs post-stimulus) increased at least 1 00%. Results: 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 insu linoma in four cases and malignant insulinoma in the remaining. It is concluded that the results of this preliminary experience show the use fulness of SIPS in the preoperative localization of occult insulinomas .