In a 35-year-old womandiagnosed with insulinoma selective intraarterial calcium injection was positive for proximal gastroduodenal artery and inferior pancreaticoduodenal artery involvement preoperatively. Although non-invasive imaging studies were negative, a mass was detected at the pancreatic uncus by intraoperative ultrasonography. Gastroduodenal artery calcium injection was performed after enucleation of the tumor. Following calcium injection, the insulin level was inappropriately increased and further pancreaticoduodenectomy was performed. After excision, another tumor was detected at the head of the pancreas by histopathological examination. As shown, selective intraarterial calcium injection is useful to localize tumors preoperatively and intraoperatively. (Internal Medicine 40: 48-51, 2001) Key words: gastroduodenal artery, enucleation, pancreaticoduodenectomy,another adenoma Case ReportA 35-year-old Japanese female had episodes of loss of awareness over 10 months. She had had a traffic accident while driving alone and was brought to our hospital on May 13, 1997. Family and past histories were not remarkable. The patient weighed 57.0 kg and her body height was 158 cm (body mass index; 22.8 kg/m2). The level of consciousness was E1V2M5(by Glasgow ComaScale). Results of routine laboratory tests including blood chemistry, hemogram, and serology were normal except for a plasma glucose of 27 mg/dl (70-110 mg/dl) and an immunoreactive insulin (IRI) of 8.7 jiU/ml (0-17 |llU/ ml). Anti-insulin antibody and anti-insulin receptor antibody tests were negative. Continuous intravenous injection of 10% glucose was given to maintain a plasma glucose level of over 70 mg/dl in order to prevent hypoglycemia and associated symptoms. Then, a fasting glucose tolerance test was performed. Based upon the collected data, the biochemical criteria for the diagnosis of insulinoma were met. Namely, the patient had symptomatic hypoglycemia (plasma glucose 47 mg/ dl) with inappropriately elevated IRI (1 1 |iU/ml) (0-17 |LiU/ ml) and C-peptide (2.2 ng/ml) (0.6-2.8 ng/ml) after 6 hours. Serum levels of HCGand HCG-pwere normal. Function of the pituitary, adrenal, thyroid, and parathyroid glands were normal. Ultrasonography (US), endoscopic ultrasonography (EUS), computed tomography (CT), magnetic resonance imaging, digital subtraction angiography, and CT angiography failed to localize the tumors. There was no evidence of hepatic metastasis on CT scan or by angiography. The percutaneous transhepatic venous sampling (PTVS) was also negative. Finally, selective intraarterial calcium injection was performed. We used the method described by O'shea et al (1). A catheter was placed in the right hepatic vein close to its junction with the inferior vena cava via a femoral vein. Each artery [proximal gastroduodenal artery (GDA), inferior pancreatico-duodenal artery (IPDA), proximal splenic artery, left hepatic artery, superior mesenteric artery] was catheterized in turn. After samples were taken twice from the hepatic vein as contr...