Localization of insulinomas by selective intraarterial calcium injection

This study examines the role of selective intraarterial calcium injection and hepatic venous sampling in the localization of insulinomas. Seven patients were studied. In all cases, ultrasound and computerized tomography scans were either negative or equivocal. Calcium gluconate was injected directly into the arteries supplying the pancreas after standard selective angiography. Insulin levels were measured in samples taken from the right hepatic vein before and 30, 60, 90, 120, and 180 s after each injection. Two doses were used, 0.025 milliequivalents Ca/kg (1 mg/kg) for the first two subjects and 0.00625 milliequivalents Ca/kg (0.25 mg/kg) for the remaining five subjects. Serum insulin levels rose at least 2-fold, the proposed diagnostic rise, from basal in six subjects; one test was negative. Of the six positive studies, a diagnostic rise was seen only in one artery in five cases. One patient did not undergo surgery. In the remaining five patients, surgery confirmed the position and histology of the tumor. The one patient with a diagnostic rise in more than one artery, however, had residual disease after surgery. The seventh subject referred specifically for localization had a negative calcium stimulation study and a subsequent diagnosis of intermittent sulfonylurea abuse was made after a positive screen. The present study shows that preoperatively, selective intraarterial calcium injection with hepatic venous sampling is a powerful technique for the localization of insulinomas. Smaller doses of calcium than previously reported can be used and may reduce the risk of hypoglycemia during the procedure.