ABSTRACT
The diagnosis of insulinoma is made primarily by the detection of an inappropriately elevated serum insulin level in the presence of a low blood glucose level. The successful resection of insulin-secreting islet cell turnors is greatly facilitated by accurate preoperative localization. But, the modalities of ultrasonography, computer tomography, magnetic resonance imaging and selective arteriography often fail to detect insulinoma smaller than 1.5 cm in diameter. In this report, we describe a patient with an insulinoma successfully localized by percutaneous transhepatic portal vein sampling but not by abdominal ultrasonography, computer tomography and selective arteriography. Percutaneous transhepatic portal vein catheterization with insulin sampling showed sudden step-up of insulin concentrations near 6 cm from distal splenic vein. During operation, a 1×1.3cm sized tumor was found at the junction of body and tail of pancreas, so distal pancreatectomy was performed, We propose that preoperative percutaneous transhepatic portal vein catheterization with measurement of radioimmunoactive insulin concentration is a safe and reliable method and plays an important role to localize insulinoma that are considered occult after conventional diagnostic studies have been negative.